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.
The nations who either had or wanted to have colonies in the New World or Africa wanted these colonies to bring them a massive amount of natural resources and riches, such as cotton, tobacco, gold, silver, etc--which were wildly profitable.
Human sacrifice was the most common. They would sacrifice humans to Aztec God's. Several Aztec's would sacrifice prisoners from war.
I hope this helps!
~cupcake
"The Truman Doctrine was an American foreign policy whose stated purpose was to counter Soviet geopolitical expansion during the Cold War."
