What does nationalism have to do with World War 1?

the answer is

Nationalism was a prominent force in early 20th century Europe and a significant cause of World War I. Nationalism is an intense form of patriotism or loyalty to one’s country. Nationalists exaggerate the importance or virtues of their home country, placing its interests above those of other nations.

after the civil war, and with the termination of slavery, the south was faced with a big problem; what was supposed to happen and how they were supposed to deal with the freedom and the rights that black people and freed slaves had gained as a result of the north defeating the south and forcing the end of slavery. first, most, if not all, of the workforce of the south came from slaves and they did not have an option to replace the loss of said workforce. second, particularly in the south, people were convinced that black people were lesser, less intelligent, less capable and less smart than whites. this posed a huge problem for them. also, southerners were faced with another issue; freed slaves now had a say in how their lives would be lived and the right to politically choose the way they would be governed. people in the south did not want to accept this, none of this and this opposition and the conflicts that arose from it, not to mention the afereffects of the war, forced the congress of the time to enact and enforce the reconstruction plans that had been proposed by president andrew johnson.

hello!

according to the passage the most suitable options are two. the first one is "by leading the aef to victory in several key battles" like the battle of saint- mihiel and the battle of cantigny mentioned in the passage you copied here. the second one is "by the aef and allied forces defeat germany" since the passage says that his army destroy the german resistance in the meuse- argonne offensive. and also, "by insisting that the aef operate as an independent force".

hope this