A Roman legion (from Latin legio "military levy, conscription", from legere "to choose") normally indicates the basic ancient Roman army unit recruited specifically from Roman citizens. In reference to the early Roman Kingdom (as opposed to the Roman Republic or Empire), "the legion" means the entire Roman army.
The Federalist Papers were written to convince Americans to approve the U.S. Constitution.
The answer is true, and the book he wrote is called "The Jungle", which he wrote in 1906.
The United States sent military forces to the Balkans during the 1990s in order to rescue people from atrocities committed against them--"crimes against humanity"--and to take the assertive action that NATO as a peace-keeping enterprise could not take to end the war.