Generally speaking, the main focus of U.S. foreign-policy making is on ensuring that the United States stays safe from attack, but there are other motivations (humanitarian, economic, etc.) as well.
The map above shows what Europe’s borders looked on the eve of World War One in 1914, overlaid on top of the borders of European countries today. ... The Austro-Hungarian Empire and Russian Empires in particular controlled most of the today’s Central and Eastern European states.
The Schlieffen Plan was created in World War 1. It was used by the Germans to in order to fight France and Russia in the war. Germany was one of the central powers and was therefore in the "middle" of France and Russia. Russia was allied with France, so once a country declared war on France, the Russian army had to pitch in and help them fight.
Furthermore, the Germans declared war on France and Russia was ready to mobilize.
While Russia was mobilizing, the Germans wanted to fight one front at once quickly, so they could then fight Russia. They had to march through neutral Belgium and encircle the French army.
