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Just focus on how each nation became more isolated and wanted to build up their own nation militarily, diplomatically, economically, etc. England would be a good choice, France, Austria, but definitely focus on Germany. Germany wanted "their place int the sun". This refers to imperialism around the world like Africa and the Oriental Pacific. So Germany began building a navy to rival Great Britain's nationalist fueled navy. Germany sudo-allied with Italy in order to have ports in the Mediterranean. Germany and Austria became involved in every Balkans incident they could in order to gain more land, take advantage of the crumbling Turkish empire and to prevent Russian expansion, most notably in the Dardanelles Straits (around Constantinople).
Doing what is best for your country no matter what the impact was. Most of the eastern Europe fell to Nationalism which would hurt minorities and immigrants. It would also cause tension between other countries that are near each other.