You’d think that as the world got more modern, we’d find ways to solve our differences that didn’t involve blowing each other’s brains out. And, luckily, that’s true! But there was still plenty of horrific violence, including the deadliest wars in human history, in the 20th century, when mankind entered a period of shocking technological advancement and increasing levels of interconnectedness. Let’s take a look at some of the wars that defined the 1900s.
10. World War I
Often referred to as the Great War, World War I (1914-1918) was triggered by the chain reaction activation of a complex web of political alliances, militarism, and imperial rivalries, all kicked off by the assassination of Archduke Franz Ferdinand of Austria-Hungary.
Nationalistic pride and 19th century tactics, however, soon clashed with the reality of modern warfare. The carnage was so severe that it forced men on all sides to dig down into the mud in order to survive. Trench warfare has thus come to symbolize the conflict as a whole. Machine guns, advanced artillery, poison gas, tanks, and aircraft all made their battlefield debuts and contributed to staggering casualties and a seemingly endless succession of failed offensives on all sides. The Eastern Front witnessed fluid and dynamic battles, while the conflict in the Middle East, Africa, and Asia added global dimensions. The war ended with an Allied victory in 1918, the signing of an Armistice, and the Treaty of Versailles in 1919. To this day, the war is often looked at as even more wholly unnecessary and tragic than other wars.
9. Russian Civil War
The Russian Civil War unfolded between 1918 and 1922, and was kicked off by the Russian Revolution of 1917. It marked a struggle for power and ideology among various factions, primarily the Bolshevik Red Army, anti-Bolshevik White Army, regional nationalist forces, and foreign interventionist troops.
The conflict began with the Bolsheviks, led by Vladimir Lenin, trying to consolidate national power after the October Revolution in 1917, during World War I. Opposition to the Bolsheviks coalesced into the White Army, composed of diverse elements ranging from monarchists to liberal democrats, seeking to resist a communist takeover.
The frontlines of the Russian Civil War stretched across vast expanses, from the Western borders to Siberia. The Red Army, despite facing internal and external challenges and numerous setbacks, ultimately secured victory. The Russian empire therefore fell. The Soviet Union took its place, and would last until the end of the Cold War in 1991.
8. Spanish Civil War
In the same way that the Mexican American War served as a proving ground for many of the tactics and commanders who’d later define the American Civil War, the Spanish Civil War – fought from 1936-1939 – gave the great powers of Europe a chance to test their mettle before being thrown into the furnace of World War II.
The war erupted when General Francisco Franco, leading a coalition of conservative, monarchist, and fascist forces, sought to overthrow the democratically elected Second Spanish Republic. The conflict was characterized by a deep ideological divide, with the Republicans, a coalition of left-wing and anti-fascist forces, opposing Franco’s Nationalists. The International Brigades, composed of volunteers from various countries, including anti-fascist activists and intellectuals, joined the Republicans. Meanwhile, Nazi Germany and Fascist Italy supported Franco’s Nationalists.
Like all wars in the first half of the 20th century, this one was particularly savage. It was defined by roughly equal numbers and frontline stalemate until close to the end of the conflict, when the nationalists surged forward and destroyed the remaining Republicans. It was one of the first times the world saw the brutality of fascism firsthand.
7. World War II
The largest, most widespread, and deadliest war in history, World War II (1939-1945) was defined by the violent expansion of the Axis Powers (Nazi Germany, Fascist Italy, Imperial Japan, and their allies) followed by counterattacks by the Allies (Britain & Commonwealth forces, France, the Soviet Union, China, the United States, and their allies), and Allied victory. The vast majority of the world was involved. As many as 85 million people, a large majority of them Allied civilians, were killed. Attacks against civilians were carried out by both sides. The Allies did this mainly via aerial bombing, including firebombing and nuclear bombing, as a way of breaking the enemy’s will to resist. The Axis mainly used ground forces to carry out bloody genocides, including the Holocaust, in which 6 million Jews were murdered by the Nazis and their partners.
The war raged from the Pacific Ocean to the jungles of southeast Asia, the Russian steppe, Sahara, and the beaches of France. It saw massive technological leaps forward, brought an end to centuries of European geopolitical dominance, and saw the rise of the United States and the Soviet Union as rival superpowers, making it arguably the single most significant event in human history.
6. Chinese Civil War
The Chinese Civil War raged between 1927 and 1949, between the Nationalist Party and the Communists. The initial phase of the Chinese Civil War began in 1927, when Chiang Kai-shek, leader of the Nationalists, turned against the Communists, leading to a violent purge known as the Shanghai Massacre. The conflict then entered a period of intermittent truces and alliances, with both sides nominally cooperating against the Japanese invasion during the Second Sino-Japanese War (1937-1945).
After Japan’s defeat in World War II, the resumption of the civil war in 1946 saw the Nationalists and Communists vie for control of China. The Communists, led by Mao Zedong, garnered widespread support among peasants, while the Nationalists struggled with corruption and inefficiency. The decisive turning point came in 1949 when the Communists emerged victorious, leading to the establishment of the People’s Republic of China on October 1, 1949. Chiang Kai-shek’s Nationalists retreated to Taiwan, where they continued to rule, while the mainland underwent significant political, economic, and social transformation under Communist rule. The Chinese Civil War had profound implications for the course of Chinese history and the global balance of power during the Cold War era and beyond.
5. Korean War
The Korean War unfolded from 1950 to 1953 on the Korean Peninsula. The war began when Communist North Korean forces, backed by the Soviet Union and China, invaded South Korea, which was supported by the United Nations and the United States.
The conflict was triggered by the political division of Korea after Japanese occupation during World War II, with the Soviets occupying the north and the United States occupying the south along the 38th parallel. The North, led by Kim Il-sung, sought to reunify the peninsula under communist rule, while the South, led by Syngman Rhee, aimed to maintain independence.
The war saw significant involvement from international forces, with the United Nations sending a multinational coalition, primarily composed of U.S. troops, to support South Korea. In response, China intervened on the side of North Korea, escalating the conflict. The war’s frontlines fluctuated along the 38th parallel, with intense fighting and trench warfare reminiscent of World War I. The armistice agreement signed in 1953 established a demilitarized zone near the original border, solidifying the division between North and South Korea. However, a formal peace treaty was never signed, and the Korean Peninsula remains divided to this day.
4. Six-Day War
The Six-Day War, a brief but transformative conflict in the Middle East, took place from June 5 to June 10, 1967, involving Israel and its neighboring Arab states. The tensions leading to the war had been escalating due to territorial disputes, political tensions, and military buildups in the region.
The immediate catalyst for the war was the closure of the Straits of Tiran by Egypt, effectively cutting off Israel’s access to the Red Sea. Additionally, Arab rhetoric and troop movements had heightened the sense of an impending conflict. In a pre-emptive strike, Israel launched Operation Focus, targeting Egyptian airfields, which resulted in the destruction of a significant portion of the Egyptian air force.
In the ensuing six days, Israel swiftly secured victories on multiple fronts. Israeli forces seized the Sinai Peninsula from Egypt, the West Bank and East Jerusalem from Jordan, and the Golan Heights from Syria. The war reshaped the political and territorial landscape of the region, marking a turning point in the Arab-Israeli conflict.
The aftermath of the Six-Day War had lasting implications. Israel’s victory significantly expanded its territorial control, leading to occupation and settlement activities in the captured territories. However, the war also intensified regional hostilities.
3. Iran-Iraq War
The Iran-Iraq War, one of the longest and bloodiest conflicts of the 20th century, took place between 1980 and 1988, involving the Islamic Republic of Iran and Saddam Hussein’s Iraq. The war had deep-seated roots in territorial disputes, historical grievances, and ideological differences.
The conflict began when Iraq, under Saddam Hussein, invaded Iran in September 1980, seeking to exploit what it perceived as Iran’s weakened position after the Iranian Revolution and the subsequent political turmoil. The war quickly escalated, with both sides engaging in WWI-style trench warfare. The conflict saw the extensive use of chemical weapons, causing significant human suffering and long-term health consequences.
The war’s dynamics were complex, with shifting alliances and international involvement. Various countries supported either Iran or Iraq, with the United States and the Soviet Union supplying arms to Iraq (weirdly enough) at different points in the conflict. The war finally concluded in 1988 with a UN-brokered ceasefire.
The Iran-Iraq War had profound consequences for both nations. It resulted in immense human and economic losses, with estimates of casualties ranging from hundreds of thousands to over a million.
2. Vietnam War
The Vietnam War, spanning from 1955 to 1975, was a protracted conflict involving Ho Chi Minh’s Communist North Vietnam, supported by the Soviet Union and China, and Ngo Dinh Diem’s South Vietnam, backed by the United States and its allies. The war was rooted in the struggle for control of Vietnam, complicated by Cold War geopolitics and ideological differences.
The war witnessed guerrilla warfare tactics by the communist forces, including the Viet Cong, and intensive bombing campaigns by the United States. The use of chemical defoliants, most notably Agent Orange, had severe environmental and health consequences. The conflict also spilled over into neighboring countries, with the US conducting arguably illegal bombings in Laos and Cambodia.
As public opposition to the war grew in the United States, a gradual withdrawal of American troops began in the early 1970s. The Paris Peace Accords in 1973 aimed to end US involvement, leading to a ceasefire. However, the war continued between North and South Vietnam, culminating in the fall of Saigon in 1975, leading to reunification under communist rule.
1. Cold War
Although (thankfully) not a war in the traditional sense, the Cold War was a geopolitical, ideological, and military standoff between the United States and its allies, representing the democratic and capitalist Western bloc, and the Soviet Union and its allies, representing the communist Eastern bloc, that persisted from the end of World War II in 1945 until the dissolution of the Soviet Union in 1991. This ideological confrontation was characterized by intense political and military rivalry, violent proxy wars around the globe, a nuclear arms race that had the world on edge for decades, a space race, and ideological competition between capitalism and communism.
The origins of the Cold War can be traced to the differing post-war visions of the Allies. While they had been wartime allies against Nazi Germany, the ideological differences and spheres of influence soon emerged. The division of Germany, the establishment of the Iron Curtain in Europe, and the containment policy formulated by the United States, deepened tensions.
The Cold War concluded with the dissolution of the Soviet Union in 1991, symbolized by the fall of the Berlin Wall in 1989. The United States emerged as the sole superpower and the beginning of a new era of international relations.