Depends on what year, if WWII then I would say the strong industrial economy due to the fact Adolf helped the people of Germany rise from depression and had people working again, living good lives, at the same time secretly rebuilding Germany's army.
3)Presidential Line of Succession
Nationalism in the Balkans in the late 19th century led to a number of nations gaining their independence from the Ottoman Empire.
The Iranian hostage crisis corresponds a the events