World War I Museum opens in Kansas City, Mo. [audio 5min]

World War I was a cataclysm that destroyed the old world order, killed at least 9 million combatants, and vaulted the United States into world prominence. But the conflict, with its trench warfare and devastating new weapons, has been largely overshadowed by World War II. The hard lessons of the "Great War" are on display at the National World War I Museum in Kansas City, Mo., which opened this weekend.