The U.S. entered the war in 1917 with the Allies after discovering that Germany had encouraged Mexico to fight the U.S. More than four million Americans fought in the war. Of these, 116,000 died and 200,000 were wounded. The war was notable for using more advanced industrial technology than any previous war, leading to high numbers of casualties. The war also had major effects on the home front. During the war, women joined the work force in greater numbers than ever before, helping create a momentum which led to the legalization of female suffrage under the 19th Amendment in 1920. The industry production in America boomed. Manufacturers had to keep production up to the pace needed to support the war. In order to produce more material in a short amount of time, there were lots of new technologies that were developed to help manufacturers meet the needs of the government and people to support the war. Also more employment opportunities opened for women and African-Americans. Women became the main population of the factories, and African-Americans migrated to the cities to find jobs. As the war ended, and soldiers started to return home, the industry production began to slow, and there was less need for workers in factories. Many women stopped working, but even so there were not enough jobs for the men returning home from Europe. This rising unemployment led to the Great Depression.