Germany was unhappy because it lost WWI, and lost land and priveledges due to Treaty of Versailles. Italy was unhappy because they joined the Allies in WWI at the last minute, hoping to gain land after winning the war.
an attempt to get Britain to stop seizing American ships.
Us victory in the mexican american war in 1848
He followed the advice of Arius Didymus who told him that "Too many Caesars is not good". (no joke I swear he actually said that) Hope this helps ;)