What role did warfare play in the various nineteenth-century nation-building efforts?

on april 6, 1917, the u.s. joined its allies--britain, france, and russia--to fight in world war i. under the command of major general john j. pershing, more than 2 million u.s. soldiers fought on battlefields in france.

napoleon the third became a empire in 1873 also known as the era of the franco-prussian war.