I would say alliances and nationalism because nationalism only encouraged countries to go to war and prove that they were the best most powerful country around and in terms of WWI, nationalism led to strong dedication to the army and just keep most countries in the war longer than they should have been in it. Alliances were significant in the exact beginning of the war and the scale to which the war was fought. The many (secret) alliances led to austria-hungary and Serbia to sorta threaten each other, which brought Germany in, then France, etc.
It ended with the destruction of the Abbasid caliphate when hugelu khan sacked Baghdad in 1258
The principle of Federalism is most reflected in the US Government & the Constitution's limits on the Federal Government's powers and the reservation of powers for the States. This is set forth clearly in the 10th amendment.
Federalism is evident throughout Government. An example of the US Department of Education. Education is a power reserved to the States and so the US Department of Education funds projects and ensures equity but the power to set curriculums is done by the States.
