This map shows the two sides of the world. The central powers were Germany Austria Hungary and Turker, and the allied powers were France Russia Serbia Italy and England. Lots of other countries got involved, because the war needed support
Nationalism was NOT a cause for World War That's propaganda shoved down our throats by globalists. United States was strongly nationalistic at the time but held an isolationist stance. Thus US did not enter the war for three years. Learn your history!
As a writer, your job is to torture your readers with tension. The fun of fiction is anticipation, and if your story doesn't have it your readers won't stick around. Here are 3 ways you might be killing your story's tension and losing readers.