Answer:
Forr starters, we know neither plague nor depression make war impossible. World War I ended just as the 1918–1919 influenza was beginning to devastate the world, but that pandemic didn't stop the Russian Civil War, the Russo-Polish War, or several other serious conflicts. The Great Depression that began in 1929 didn't prevent Japan from invading Manchuria in 1931, and it helped fuel the rise of fascism in the 1930s and made World War II more likely.