The Major Wars and Conflicts of the 20th Century

Most Significant Conflicts of the 20th Century

Serbian soldiers with a Howitzer during World War I.
Serbian officers with a Howitzer battery as they prepare to fire on the Austrians during the First World War. (circa 1915). (Photo by Hulton Archive/Getty Images)

The 20th century was dominated by wars and conflicts that often altered the balance of power across the globe. The 20th century saw the emergence of "total wars," such as World War I and World War II, which were large enough to encompass nearly the entire world. Other wars, like the Chinese Civil War, remained local but still caused the deaths of millions of people.

The reasons for the wars varied from expansion disputes to upsets in government to the intentional murder of an entire people.

However, they all shared one thing: an extraordinary number of deaths.

Which Was the Deadliest War of the 21st Century?

The largest and bloodiest war of the 20th century (and of all time) was World War II. The conflict, which lasted from 1939-1945, encompassed most of the planet. When it was finally over, more than 60 million people were dead. Of that enormous group, which represents about 3% of entire world population at the time, the huge majority (well over 50 million) were civilians.

World War I was also bloody, with 8.5 million military deaths plus an estimated 13 million more civilian deaths. If we were to add in the deaths caused by the 1918 influenza epidemic, which was spread by returning soldiers at the end of World War I, the WWI total would be much higher since the epidemic alone was responsible for 50 to 100 million deaths.

Third in the list of bloody wars of the 20th century is the Russian Civil War, which caused the deaths of an estimated 9 million people.

Unlike the two World Wars, however, the Russian Civil War did not spread across Europe or beyond. Rather, it was a struggle for power following the Russian Revolution, and it pitted the Bolsheviks, headed by Lenin, against a coalition called the White Army. Interestingly, the Russian Civil War was over 14 times deadlier than the American Civil War, which saw the deaths of 620,000.

The List of Major Wars and Conflicts of the 20th Century

All of these wars, conflicts, revolutions, civil wars, and genocides shaped the 20th century. Below is a chronological list of the major wars of the 20th century.

1898-1901 Boxer Rebellion
1899-1902 Boer War
1904-1905 Russo-Japanese War
1910-1920 Mexican Revolution
1912-1913 First and Second Balkan Wars
1914-1918 World War I
1915-1918 Armenian Genocide
1917 Russian Revolution
1918-1921 Russian Civil War
1919-1921 Irish War of Independence
1927-1937 Chinese Civil War
1933-1945 Holocaust
1935-1936 Second Italo-Abyssinian War (also known as the Second Italo-Ethiopian War or the Abyssinian War)
1936-1939 Spanish Civil War
1939-1945 World War II
1945-1990 Cold War
1946-1949 Chinese Civil War resumes
1946-1954 First Indochina War (also known as the French Indochina War)
1948 Israel War of Independence (also known as the Arab-Israeli War)
1950-1953 Korean War
1954-1962 French-Algerian War
1955-1972 First Sudanese Civil War
1956 Suez Crisis
1959 Cuban Revolution
1959-1973 Vietnam War
1967 Six-Day War
1979-1989 Soviet-Afghan War
1980-1988 Iran-Iraq War
1990-1991 Persian Gulf War
1991-1995 Third Balkan War
1994 Rwandan Genocide