25 Historical Decisions That Could Have Ended the World
Human history is full of choices that could have led to global catastrophe.
Table of Contents
1. The Cuban Missile Crisis: Kennedy’s Restraint
2. Stanislav Petrov’s Decision to Trust His Instincts
3. Chamberlain’s Appeasement of Hitler
4. The US Decision to Drop Atomic Bombs
5. The Austrian Ultimatum to Serbia
6. Operation Able Archer 83: NATO’s Realistic Exercise
7. The Bay of Pigs Invasion Decision
8. Khrushchev’s Decision During the Berlin Crisis
9. The Chernobyl Cover-Up Decision
10. The Treaty of Versailles Terms
11. Operation Barbarossa: Hitler’s Eastern Gambit
12. The Schlieffen Plan Implementation
13. The Zimmermann Telegram Decision
14. Manhattan Project: The Nuclear Race
15. The Ems Dispatch Alteration
16. Gorbachev’s Decision to End the Cold War
17. The Non-Proliferation Treaty Negotiations
18. The Suez Crisis Escalation
19. The Decision to Ignore Rwanda
20. The Iraq Invasion Decision
21. The Development of CRISPR Gene Editing
22. The Internet’s Military Origins
23. The Introduction of Leaded Gasoline
24. The Global DDT Ban Decision
25. The Development of Artificial Intelligence
26. Frequently Asked Questions
Human civilization hangs by a thread—a thread woven from countless decisions made by individuals, governments, and institutions throughout history. While we often celebrate the great achievements of humanity, we rarely consider how close we’ve come to total annihilation through the choices of a few key figures. These 25 historical decisions represent moments when the wrong choice could have literally ended the world as we know it, whether through nuclear war, pandemic, environmental collapse, or technological catastrophe.
Each decision on this list was made under intense pressure, with limited information, and with consequences that stretched far beyond what anyone could have imagined. Some prevented disaster through wisdom or luck, while others set in motion chains of events that brought us perilously close to the brink. Understanding these pivotal moments helps us appreciate both the fragility of our civilization and the enormous responsibility that comes with wielding power in an interconnected world.
1. The Cuban Missile Crisis: Kennedy’s Restraint (1962)
President John F. Kennedy’s decision to pursue a naval quarantine instead of military strikes during the Cuban Missile Crisis may have been the single most important choice in preventing nuclear war. When Soviet missiles were discovered in Cuba, Kennedy’s military advisors overwhelmingly recommended immediate airstrikes followed by invasion. General Curtis LeMay argued that anything less would be perceived as weakness and invite further Soviet aggression.
Kennedy chose the more measured approach of a naval blockade, giving Khrushchev room to back down while maintaining American resolve. This decision allowed for secret negotiations that included the removal of US missiles from Turkey—a face-saving measure for the Soviets that prevented the conflict from escalating to nuclear exchange.
Had Kennedy chosen the military option, the likely Soviet response would have been to defend their missiles and personnel in Cuba, potentially triggering the very nuclear war both superpowers claimed to want to avoid. Defense Secretary Robert McNamara later estimated that the chances of nuclear war during this crisis were “much greater than 1 in 3,” making Kennedy’s restraint perhaps the most consequential presidential decision in human history.
2. Stanislav Petrov’s Decision to Trust His Instincts (1983)
One man’s gut feeling averted nuclear war in 1983.
Lieutenant Colonel Stanislav Petrov’s decision to disregard a computer warning showing incoming US missiles on September 26, 1983, prevented what could have been the end of civilization. The Soviet early warning system showed five American ICBMs heading toward the USSR, but Petrov made the split-second decision that it was a false alarm.
Protocol demanded that Petrov immediately report the attack to his superiors, who would have launched a full-scale retaliatory strike against the United States. Instead, Petrov reasoned that if America were actually launching a first strike, they would send hundreds of missiles, not just five. His intuition proved correct—the alert was caused by rare sunlight conditions affecting the satellite sensors.
Petrov’s decision was particularly significant because it occurred during one of the most tense periods of the Cold War, just weeks after the Soviets had shot down Korean Air Lines Flight 007 and during NATO’s Able Archer 83 exercise, which had Soviet leaders convinced that the West was preparing for war. A different officer following protocol could have triggered automatic retaliation, leading to global nuclear war within hours.
3. Chamberlain’s Appeasement of Hitler (1938)
Appeasement seemed to avoid war but enabled a greater conflict.
Prime Minister Neville Chamberlain’s decision to appease Adolf Hitler at the Munich Conference in 1938 fundamentally altered the trajectory of the 20th century. By allowing Germany to annex the Sudetenland from Czechoslovakia without consequences, Chamberlain hoped to prevent another devastating European war. His famous declaration of “peace for our time” reflected genuine belief that diplomatic compromise could contain Nazi ambitions.
However, this decision emboldened Hitler and demonstrated to the world that aggression would be rewarded rather than punished. The Munich Agreement also eliminated Czechoslovakia’s formidable border fortifications and industrial capacity, making subsequent German expansion easier and more devastating. Most crucially, it gave Hitler additional time to rearm and prepare for a war he was planning regardless of diplomatic outcomes.
Had Britain and France chosen to confront Germany over Czechoslovakia in 1938, when Hitler’s military was still relatively weak and the Nazi regime less consolidated, World War II might have been prevented entirely—or at least limited to a much smaller conflict. Instead, appeasement made the eventual war longer, more destructive, and more likely to develop into the global catastrophe that claimed over 70 million lives.
4. The US Decision to Drop Atomic Bombs (1945)
A controversial decision that quickly ended WWII but at great cost.
President Harry Truman’s decision to use atomic weapons against Japan represented the first and only time nuclear weapons have been used in warfare, establishing a precedent that has shaped international relations ever since. The immediate justification was to avoid the massive casualties expected from Operation Downfall, the planned invasion of Japan, which military estimates suggested could cost over a million American lives and several million Japanese casualties.
However, the decision also served as a demonstration of American power to the Soviet Union and the world. By choosing to use both available bombs (on Hiroshima and Nagasaki) rather than conducting a demonstration or using just one, Truman sent an unmistakable message about American nuclear capabilities and willingness to use them.
This decision launched the nuclear age and the arms race that would define the Cold War. Had Truman chosen differently—perhaps accepting Japan’s conditional surrender or conducting a demonstration detonation—the nuclear taboo might never have been broken. The world might have developed different norms around nuclear weapons, potentially preventing the decades of nuclear brinksmanship that followed. Alternatively, delaying nuclear weapons’ first use might have led to their eventual use in an even more catastrophic context, such as the Korean War or Berlin Crisis.
5. The Austrian Ultimatum to Serbia (1914)
Austria-Hungary’s decision to issue an intentionally unacceptable ultimatum to Serbia following the assassination of Archduke Franz Ferdinand transformed a regional crisis into a world war. The ultimatum, drafted with German encouragement, contained ten demands so harsh that acceptance would have effectively ended Serbian sovereignty. When Serbia accepted nine of the ten demands but requested arbitration on the most severe point, Austria-Hungary declared this insufficient and declared war.
This decision activated the web of alliances that turned a Balkan conflict into World War I. Russia mobilized to support Serbia, Germany declared war on Russia to support Austria, France was drawn in through its alliance with Russia, and Britain entered to defend Belgian neutrality. What began as a diplomatic crisis between two relatively minor powers escalated into a global conflict that killed over 16 million people and reshaped the world order.
Had Austria-Hungary chosen a more measured response—perhaps accepting international mediation or being satisfied with Serbia’s substantial concessions—the Great War might have been avoided entirely. The subsequent Russian Revolution, rise of fascism, and World War II all stemmed directly from the instability and resentment created by the First World War, making this ultimatum one of the most consequential documents in human history.
6. Operation Able Archer 83: NATO’s Realistic Exercise (1983)
NATO’s decision to conduct an extremely realistic nuclear war simulation in November 1983 nearly triggered the actual nuclear conflict it was meant to prepare for. Operation Able Archer 83 was designed to test NATO’s command and control procedures during a simulated escalation from conventional to nuclear warfare. However, the exercise was so authentic that Soviet intelligence believed it might be cover for an actual first strike.
The simulation included realistic political tensions, authentic communication protocols, and the participation of high-level officials including President Reagan. To Soviet observers already convinced that the West was preparing for war, these elements appeared to confirm their worst fears. KGB residencies across Europe went on high alert, and Soviet nuclear forces were placed on enhanced readiness.
What made this particularly dangerous was the context: US-Soviet relations were at their lowest point since the Cuban Missile Crisis, the Soviets had recently shot down KAL Flight 007, and Reagan’s military buildup and “evil empire” rhetoric had convinced many Soviet leaders that America was preparing for war. Had the exercise included additional realistic elements or been conducted during an actual crisis, it could have triggered a Soviet preemptive strike based on the mistaken belief that NATO was launching an attack.
7. The Bay of Pigs Invasion Decision (1961)
President Kennedy’s decision to authorize the CIA-backed invasion of Cuba in April 1961 nearly triggered a nuclear confrontation just three months into his presidency. The plan, inherited from the Eisenhower administration, called for 1,400 Cuban exiles to land at the Bay of Pigs and overthrow Fidel Castro’s government. Kennedy approved the operation but refused to provide US air support, dooming it to failure.
The invasion’s failure had profound consequences beyond the immediate humiliation. It pushed Cuba firmly into the Soviet camp and convinced Castro that he needed nuclear weapons to deter future American attacks. This directly led to the Cuban Missile Crisis eighteen months later, when Soviet missiles were discovered just 90 miles from Florida.
Had Kennedy either provided full support to ensure the invasion’s success or canceled it entirely, the Cuban Missile Crisis might never have occurred. A successful invasion would have eliminated the communist threat in America’s backyard but might have triggered immediate Soviet retaliation elsewhere. Canceling the operation might have preserved the possibility of negotiated coexistence with Castro, preventing Cuba’s transformation into a Soviet military outpost that brought the world to the brink of nuclear war.
8. Khrushchev’s Decision During the Berlin Crisis (1961)
Soviet Premier Nikita Khrushchev’s decision to build the Berlin Wall rather than attempt to force the Western powers out of Berlin prevented what could have escalated into nuclear war. Since 1958, Khrushchev had been demanding that the Western powers withdraw from West Berlin, threatening to sign a separate peace treaty with East Germany that would terminate Western access rights to the city.
By 1961, the crisis had reached a boiling point. Over 3 million East Germans had fled to the West through Berlin since 1949, creating a massive brain drain that threatened the East German state’s viability. Khrushchev faced pressure from hardliners to take decisive action, while Kennedy had made clear that any attempt to force the West out of Berlin would be met with military resistance.
Khrushchev’s decision to seal the border with a wall solved the immediate refugee problem without directly challenging Western rights in Berlin. Though brutal and dividing families overnight, the wall prevented the escalation that could have led to nuclear confrontation over Berlin. Had Khrushchev chosen to directly challenge Western access or attempt to force a Western withdrawal, the result could have been the nuclear war that both superpowers had managed to avoid during the more famous Cuban Missile Crisis.
9. The Chernobyl Cover-Up Decision (1986)
The Soviet government’s initial decision to downplay and cover up the Chernobyl nuclear disaster nearly led to a catastrophe that could have made vast areas of Europe uninhabitable. When Reactor 4 exploded on April 26, 1986, Soviet officials initially denied the severity of the accident, delayed evacuation of nearby areas, and provided false information to other countries about radiation levels.
This decision to prioritize secrecy over safety meant that critical early response measures were delayed. The evacuation of Pripyat didn’t begin until 36 hours after the explosion, exposing thousands of people to unnecessary radiation. Other European countries weren’t warned about radioactive fallout crossing their borders, preventing them from taking protective measures for their populations.
Most dangerously, the cover-up delayed international assistance that might have prevented the disaster from becoming far worse. If the reactor’s graphite fire had reached the other reactors at the plant, or if the molten core had reached groundwater and caused a massive steam explosion, the contamination could have been orders of magnitude greater. The decision to finally reveal the truth and accept international help, made after Swedish monitors detected abnormal radiation levels, may have prevented an environmental catastrophe that could have made central Europe uninhabitable for centuries.
10. The Treaty of Versailles Terms (1919)
The Allied decision to impose harsh terms on Germany in the Treaty of Versailles created the conditions that would lead to an even more devastating world war just two decades later. The treaty stripped Germany of territory, imposed massive reparations, limited its military to token forces, and included a “war guilt” clause that placed full responsibility for the war on Germany and its allies.
While the desire to punish Germany and prevent future aggression was understandable, the treaty’s harshness created deep resentment among the German population and made democratic government nearly impossible. The reparations payments destabilized the German economy, contributing to hyperinflation and the Great Depression’s severe impact on Germany. This economic chaos created the conditions that allowed Adolf Hitler to rise to power by promising to restore German greatness and overturn the “unjust” treaty.
Had the Allies chosen a more moderate approach—similar to the Congress of Vienna after Napoleon’s defeat—Germany might have been reintegrated into the European community without the resentment that fueled Nazi ideology. A Germany that felt fairly treated might have developed into a stable democracy, preventing World War II and the Holocaust. Instead, the treaty’s harshness created a desire for revenge that Hitler skillfully exploited, leading to a war even more destructive than the one the treaty was meant to prevent.
11. Operation Barbarossa: Hitler’s Eastern Gambit (1941)
Hitler’s decision to launch Operation Barbarossa, the invasion of the Soviet Union, while still fighting Britain fundamentally changed the character and outcome of World War II. By opening a two-front war, Hitler ensured that Germany would face the combined industrial might of the Soviet Union, British Empire, and eventually the United States—a coalition that would prove impossible to defeat.
The decision was driven by Hitler’s ideological obsession with destroying “Jewish Bolshevism” and acquiring Lebensraum (living space) for the German people. However, from a strategic standpoint, it was disastrously premature. Germany had not yet defeated Britain, and the invasion was launched later than planned due to the Balkan campaign, ensuring that German forces would face the Russian winter unprepared.
Had Hitler chosen to consolidate his European conquests, defeat Britain, or at least secure a separate peace before turning east, the war’s outcome might have been very different. A Germany that controlled all of Europe’s resources and faced only a single front against the Soviet Union might have been impossible to defeat. Alternatively, Hitler could have avoided war with the USSR entirely, potentially allowing Nazi Germany to dominate Europe for decades while developing nuclear weapons and other advanced technologies that could have made it truly invincible.
12. The Schlieffen Plan Implementation (1914)
Germany’s decision to implement the Schlieffen Plan, which required invading France through Belgium, directly caused Britain’s entry into World War I and transformed a continental conflict into a global war. The plan called for a rapid defeat of France before turning to face Russia, but its requirement to violate Belgian neutrality triggered Britain’s guarantee to defend Belgium.
The decision to proceed with the plan despite knowing it would bring Britain into the war reflected German leadership’s fatal miscalculation about British resolve and the plan’s feasibility. German leaders believed that Britain’s small professional army couldn’t significantly impact a continental war and that France could be defeated before British forces became relevant.
Instead, British entry brought the Royal Navy’s blockade, the British Empire’s resources, and eventually American participation into the war against Germany. Had Germany chosen to attack France directly or developed a plan that respected Belgian neutrality, Britain might have remained neutral, fundamentally altering the war’s balance. A World War I without British participation would have been shorter, less destructive, and might have ended with German victory—preventing the conditions that led to the Russian Revolution, rise of fascism, and World War II.
13. The Zimmermann Telegram Decision (1917)
German Foreign Secretary Arthur Zimmermann’s decision to propose a German-Mexican alliance against the United States provided the final push that brought America into World War I. The telegram, sent in January 1917, proposed that if the United States entered the war against Germany, Mexico should become Germany’s ally and would receive financial support and recover Texas, New Mexico, and Arizona after victory.
The telegram was intercepted and decoded by British intelligence, which shared it with the American government. When published in American newspapers, it caused outrage and helped convince a previously reluctant Congress to declare war on Germany. American entry fundamentally changed the war’s outcome, providing the fresh troops and industrial capacity needed to defeat the Central Powers.
Had Zimmermann chosen not to send the telegram, or had it not been intercepted, American entry into the war might have been delayed or avoided entirely. Without American participation, the war might have ended in stalemate or Central Powers victory, completely changing the 20th century’s trajectory. The Russian Revolution might have succeeded differently, there would have been no Versailles Treaty, and the conditions that led to World War II would never have developed.
14. Manhattan Project: The Nuclear Race (1942-1945)
The Allied decision to pursue nuclear weapons through the Manhattan Project represented a race that, if lost, could have led to Nazi or Japanese nuclear dominance and fundamentally different war outcomes. President Roosevelt’s decision to approve the massive industrial undertaking in 1942 was driven by fears that Germany was developing nuclear weapons and could win the war through atomic bombs.
The project ultimately employed over 130,000 workers and cost over $2 billion (equivalent to about $30 billion today), making it one of the largest scientific endeavors in human history. The decision to pursue nuclear weapons with such dedication and resources proved crucial when intelligence later revealed that Germany was indeed working on atomic weapons, though their program was further behind than initially feared.
Had the Allies chosen not to pursue nuclear weapons, or had they lost the nuclear race to the Axis powers, World War II could have had a very different outcome. A Nazi Germany or Imperial Japan armed with nuclear weapons might have been able to force Allied surrender or at least negotiate a more favorable peace. The decision to win the nuclear race may have prevented decades or centuries of fascist domination, though it also introduced the existential threat that has shadowed humanity ever since.
15. The Ems Dispatch Alteration (1870)
Otto von Bismarck’s decision to alter the Ems Dispatch, making it appear that the Prussian king had insulted the French ambassador, deliberately provoked France into declaring war on Prussia and unified Germany through conflict. The original telegram was a polite account of a diplomatic meeting, but Bismarck’s edited version made it seem like a deliberate snub that demanded French response.
This manipulation successfully goaded Napoleon III into declaring war, allowing Bismarck to present Prussia as the victim of French aggression and rally all German states to Prussia’s side. The resulting Franco-Prussian War led to German unification under Prussian leadership and established Germany as Europe’s dominant power.
Had Bismarck chosen not to alter the dispatch, the diplomatic crisis might have been resolved peacefully, preventing both the Franco-Prussian War and German unification. Without a unified Germany challenging European balance, the alliance system that led to World War I might never have developed. France would have remained Europe’s dominant continental power, and the entire trajectory of European history would have been fundamentally different. The decision to manipulate a single telegram thus set in motion events that would ultimately lead to two world wars and the transformation of the global order.
16. Gorbachev’s Decision to End the Cold War (1985-1991)
Mikhail Gorbachev’s decision to pursue glasnost and perestroika, ultimately leading to the Cold War’s end, prevented what many believed was an inevitable nuclear conflict between the superpowers. When Gorbachev assumed power in 1985, the Soviet Union was economically stagnant, technologically falling behind, and increasingly unable to compete with American military spending, particularly Reagan’s Strategic Defense Initiative.
Gorbachev chose to pursue radical reforms and seek accommodation with the West rather than escalate the arms race or attempt to maintain Soviet control through force. His decisions to allow Eastern European countries to choose their own paths, withdraw from Afghanistan, and pursue arms control agreements with the United States fundamentally changed the global strategic balance.
Had Gorbachev or his potential hardliner successors chosen to maintain confrontation with the West, the result could have been catastrophic. A Soviet Union facing economic collapse might have chosen war rather than accept defeat, or internal instability could have led to loss of control over nuclear weapons. Instead, Gorbachev’s peaceful approach ended the Cold War without the nuclear exchange that many experts considered inevitable, though it came at the cost of the Soviet Union’s existence.
17. The Non-Proliferation Treaty Negotiations (1968)
The international decision to create and sign the Nuclear Non-Proliferation Treaty represented a crucial choice to prevent the spread of nuclear weapons to additional countries. In the 1960s, experts predicted that dozens of countries would develop nuclear weapons by the 1980s, creating an unstable multipolar nuclear world where accidental or intentional nuclear use would be nearly inevitable.
The treaty established a bargain: non-nuclear states agreed not to develop weapons in exchange for access to peaceful nuclear technology and a commitment from nuclear powers to eventually disarm. While imperfect, the treaty has been remarkably successful in limiting proliferation—only nine countries possess nuclear weapons today instead of the 20-30 that were predicted.
Had the international community chosen not to pursue nonproliferation, the world today would be far more dangerous. A world with nuclear weapons in the hands of dozens of countries, including unstable regimes and non-state actors, would have likely experienced nuclear use by now. The decision to create legal and political barriers to proliferation, backed by monitoring and enforcement mechanisms, may have prevented nuclear weapons from being used in regional conflicts that have occurred since 1968.
18. The Suez Crisis Escalation (1956)
Britain and France’s decision to collude with Israel in attacking Egypt during the Suez Crisis nearly triggered a broader conflict involving nuclear-armed superpowers. When Egyptian President Nasser nationalized the Suez Canal, Britain and France secretly agreed to have Israel attack Egypt, providing them with a pretext to intervene “to separate the combatants” and retake the canal.
The operation was a diplomatic disaster that exposed the deception and prompted harsh condemnation from both the United States and Soviet Union. Most dangerously, Soviet Premier Bulganin threatened to use nuclear weapons against Britain and France if they didn’t withdraw, while also threatening to send “volunteers” to help Egypt—potentially bringing Soviet forces into direct conflict with NATO allies.
Had Britain and France chosen to continue their operation despite superpower opposition, or had they coordinated with the United States beforehand, the crisis could have escalated into nuclear confrontation. The decision to back down when faced with superpower opposition, while humiliating for the former colonial powers, prevented what could have been the first nuclear conflict of the Cold War and established the principle that even allies couldn’t act unilaterally in the nuclear age.
19. The Decision to Ignore Rwanda (1994)
The international community’s decision not to intervene in the Rwandan genocide, despite clear evidence of systematic mass murder, demonstrated how inaction can be as consequential as action. The United Nations had peacekeepers in Rwanda when the genocide began, but they were ordered not to intervene and were actually reduced in number as the killing intensified.
The United States, still traumatized by the Somalia intervention’s failure, specifically avoided using the term “genocide” because it would legally require intervention under international law. Other major powers similarly avoided action, calculating that they had no vital interests at stake in a small African country.
The decision to prioritize political calculations over humanitarian concerns allowed the murder of approximately 800,000 people in just 100 days. More broadly, it established a precedent of inaction in the face of genocide that has been repeated in subsequent crises. Had the international community chosen to intervene decisively, it could have prevented the genocide and established stronger norms around the “responsibility to protect” that might have prevented subsequent humanitarian catastrophes in the Balkans, Syria, and elsewhere.
20. The Iraq Invasion Decision (2003)
The US decision to invade Iraq in 2003, based on flawed intelligence about weapons of mass destruction, destabilized the Middle East and contributed to the rise of ISIS, ongoing regional conflicts, and hundreds of thousands of deaths. The invasion was justified as preventing Saddam Hussein from using or sharing WMDs with terrorists, but no such weapons were found.
The decision to invade without UN approval and based on disputed evidence fractured the Western alliance and undermined international law. More immediately, the poorly planned occupation that followed the invasion’s military success created a power vacuum that led to sectarian civil war, the rise of Al-Qaeda in Iraq (later ISIS), and ongoing instability that has spread throughout the region.
Had the United States chosen to continue containment rather than invasion, or had they planned adequately for post-invasion governance, the Middle East might be far more stable today. The invasion’s consequences have included the Syrian civil war, the European refugee crisis, and the rise of ISIS terrorism globally. The decision thus demonstrates how even well-intentioned actions based on flawed intelligence can have catastrophic unintended consequences.
21. The Development of CRISPR Gene Editing (2012)
The scientific community’s decision to develop and publish CRISPR-Cas9 gene editing technology created unprecedented power to modify life itself, including the potential to create biological weapons or accidentally release harmful genetic modifications. While CRISPR offers incredible potential to cure genetic diseases and improve crops, it also enables the creation of enhanced pathogens that could cause pandemic or the modification of organisms in ways that could disrupt ecosystems.
The technology’s relative simplicity means it can be used by smaller laboratories and potentially rogue actors, unlike nuclear weapons which require substantial infrastructure. Early concerns focused on the possibility of editing human germline cells (affecting future generations), but broader concerns include the weaponization of the technology or accidental release of harmful organisms.
The decision by the scientific community to proceed with CRISPR development while working to establish ethical guidelines represents an attempt to gain the benefits while minimizing risks. However, the technology’s power is so great that even well-intentioned use could have unforeseeable consequences. Had scientists chosen to suppress the technology or had they failed to develop appropriate safeguards, the results could range from missed opportunities to cure diseases to accidental ecological or pandemic catastrophes.
22. The Internet’s Military Origins (1969)
The US Defense Department’s decision to create ARPANET, the internet’s predecessor, fundamentally transformed human communication and created new categories of existential risk. While designed to create a communication network that could survive nuclear attack, the internet has evolved into the backbone of modern civilization—and a potential point of catastrophic failure.
The decision to base internet protocols on open, decentralized principles enabled its rapid growth and democratization but also created vulnerabilities that hostile actors could exploit. Today’s interconnected world faces risks from cyber warfare, infrastructure attacks, and the spread of misinformation that could destabilize societies or even trigger real-world conflicts.
Had the internet been designed with greater security from the beginning, or had it remained a purely military system, many current vulnerabilities wouldn’t exist. However, the open architecture that creates risks also enabled the internet’s revolutionary impact on human knowledge, communication, and economic development. The decision to prioritize functionality over security has created a world more connected but potentially more fragile than ever before.
23. The Introduction of Leaded Gasoline (1921)
The decision by General Motors to introduce tetraethyl lead as a gasoline additive, despite knowing its toxic effects, created one of the most widespread environmental and public health disasters in history. Lead poisoning from gasoline exhaust affected millions of people worldwide, reducing IQ, increasing violence, and causing numerous health problems that persisted for decades.
Thomas Midgley Jr., the engineer who developed leaded gasoline, was aware of lead’s toxicity but promoted it anyway because it solved the “engine knock” problem and was more profitable than alternative solutions. The decision to prioritize short-term profits over long-term public health had consequences that lasted for over 70 years in many countries.
Had the automotive industry chosen non-toxic alternatives (which existed but were less profitable), millions of people might have lived healthier, more productive lives. Some researchers argue that the reduction in lead exposure since the 1970s has contributed to decreased crime rates and improved educational outcomes. The decision thus demonstrates how industrial choices driven by profit can have massive unintended consequences that affect entire generations.
24. The Global DDT Ban Decision (1972)
The decision to ban DDT in many countries following Rachel Carson’s “Silent Spring” represented a choice between environmental protection and disease prevention that continues to generate controversy. DDT was highly effective at controlling malaria-carrying mosquitoes but also caused severe environmental damage, particularly to bird populations, and accumulated in the food chain.
The environmental movement’s successful campaign to ban DDT in the United States and other developed countries likely prevented ecological disaster, but the global reduction in DDT use may have contributed to malaria’s resurgence in developing countries. Critics argue that the ban has cost millions of lives, particularly in Africa, where malaria remains a leading killer.
Had countries chosen to continue unlimited DDT use, the environmental consequences could have been catastrophic, potentially including the extinction of numerous bird species and severe damage to ecosystems. However, had they developed more nuanced policies that allowed targeted use for disease control while restricting agricultural use, both environmental and public health goals might have been better served.
25. The Development of Artificial Intelligence (1956-Present)
The decision by computer scientists to pursue artificial general intelligence, despite warnings about existential risks, represents perhaps the most consequential choice currently being made. While AI offers tremendous potential benefits, including solutions to climate change, disease, and poverty, it also poses unprecedented risks if advanced AI systems become unaligned with human values or beyond human control.
The rapid pace of AI development, driven by competition between nations and companies, has outpaced the development of safety measures and governance frameworks. Some experts warn that artificial general intelligence could pose an existential threat to humanity if not properly designed and controlled, while others argue that the benefits justify the risks.
The ongoing decisions about AI development, regulation, and deployment will likely determine whether artificial intelligence becomes humanity’s greatest achievement or its final invention. Unlike previous technologies, AI has the potential to surpass human intelligence and become an independent agent with its own goals. The choices being made today about AI safety research, international cooperation, and development timelines may be as important as any decision in human history.
Frequently Asked Questions
What makes a decision “world-ending” in historical terms?
A world-ending decision doesn’t necessarily mean the literal destruction of Earth, but rather choices that could have led to the collapse of human civilization, massive loss of life, or fundamental changes that would have made our current world impossible. These include decisions that could have triggered nuclear war, caused environmental collapse, enabled totalitarian dominance, or unleashed uncontrollable technologies.
How do historians determine what might have happened if different choices were made?
Historians use counterfactual analysis, examining the forces, constraints, and alternative options that decision-makers faced at the time. They consider the immediate consequences that were avoided, the chain reactions that were prevented, and the long-term trajectories that were altered. While we can’t know with certainty what would have happened, we can assess the likelihood and potential scope of different outcomes based on historical evidence.
Were decision-makers aware of the global consequences of their choices at the time?
Most decision-makers were not fully aware of the global, long-term consequences of their choices. Many of these decisions were made under intense pressure, with limited information, and focused on immediate concerns rather than long-term implications. However, some leaders, particularly during the nuclear age, were acutely aware that their choices could affect all of humanity.
Why do some beneficial decisions appear on this list?
Several entries, like the development of the internet or CRISPR gene editing, represent beneficial technologies that also created new forms of existential risk. The decision to proceed with these developments was consequential because it opened up both tremendous opportunities and unprecedented dangers. The key insight is that transformative technologies are double-edged swords that require careful management.
How close has humanity actually come to ending civilization?
According to experts who have studied these events, humanity has come remarkably close to civilization-ending catastrophes multiple times. The Cuban Missile Crisis, Stanislav Petrov’s decision, and several other nuclear near-misses brought us within hours or minutes of nuclear war. Climate scientists argue we’re currently facing an existential threat from environmental collapse, while AI researchers warn of unprecedented risks from artificial intelligence.
What can we learn from these historical decisions to help with current global challenges?
These historical cases demonstrate the importance of international cooperation, the value of restraint and careful consideration in crisis situations, the need for robust institutions and safeguards, and the critical role that individual judgment can play in preventing catastrophe. They also show how technological developments require ethical frameworks and governance structures to manage their risks.
Are there modern decisions being made today that could belong on this list?
Yes, current decisions about climate change response, AI development, nuclear weapons policy, pandemic preparedness, and emerging biotechnologies will likely be viewed by future historians as equally consequential. The difference is that we’re living through these decisions now and can still influence their outcomes.
How do small decisions by individuals compare to major policy decisions by governments?
Some of the most consequential decisions on this list were made by individuals in critical moments—like Stanislav Petrov’s choice to trust his instincts over protocol. These cases demonstrate that individual judgment and moral courage can be just as important as grand strategy and policy decisions. They also show how the right person in the right position at the right time can change the course of history.
Understanding these 25 historical decisions helps us appreciate both how fragile human civilization is and how much depends on the wisdom, restraint, and moral courage of those who wield power. As we face new global challenges from climate change to artificial intelligence, the lessons from these historical moments become more relevant than ever. The choices we make today about emerging technologies, international cooperation, and global governance will determine whether future historians look back on our era as one of wisdom or catastrophic miscalculation.
Each generation faces decisions that seem manageable in the moment but carry consequences that echo through history. By studying how previous generations navigated their most critical choices—both successfully and unsuccessfully—we can better prepare ourselves to make the decisions that will shape humanity’s future. The thread of civilization remains fragile, but understanding its vulnerability is the first step toward protecting it.