When Yuan died, however, civil war broke out and warlords ruled amid chaos. The opium trade returned, irrigation failed, and World War I added to the general misery. Millions of peasants died due to a famine during the war. Central rule was elusive. | When Yuan died, however, civil war broke out and warlords ruled amid chaos. The opium trade returned, irrigation failed, and World War I added to the general misery. Millions of peasants died due to a famine during the war. Central rule was elusive. |