Common causes
Security fears
One side's defense looks like a threat to the other
Territory and resources
Land, water, oil and trade routes
Ideas and identity
Political, religious or national beliefs
Miscalculation
Leaders misjudge the other side's resolve
Twentieth-century conflicts
| Conflict | Years | Estimated deaths |
|---|---|---|
| World War I | 1914–1918 | About 15–20 million |
| World War II | 1939–1945 | About 70–85 million |
| Korean War | 1950–1953 | About 3 million |
| Cold War | 1947–1991 | Proxy wars; no direct U.S.–Soviet war |
Estimates vary widely among historians.
Keeping the peace since 1945
- The United NationsFounded in 1945 to resolve disputes
- Nuclear deterrenceThe cost of war between nuclear powers is too high
- AlliancesSuch as NATO, formed in 1949
- Trade tiesNations that trade heavily have more to lose
1962
The Cuban Missile Crisis brought the world close to nuclear war before both sides stepped back.
Sources: Encyclopaedia Britannica; National WWII Museum; United Nations
Remember
Wars usually come from fear, competition and miscalculation together; deterrence and diplomacy work to prevent them.
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Answer key
- When did World War II take place?1939–1945From 1939 to 1945.
- What is nuclear deterrence?The threat of devastating retaliation discourages attackThe cost of nuclear war deters it.
- When was the United Nations founded?1945In 1945, after World War II.
- Which 1962 event brought the world close to nuclear war?Cuban Missile CrisisThe Cuban Missile Crisis.
- What does 'miscalculation' mean as a cause of war?Leaders misjudging the other sideMisjudging resolve or strength can start wars.