Piracy as a crime dates to at least 1400 B.C., making it the oldest known international offense. The brilliant Roman orator Cicero described pirates as the enemies of all humankind, a designation that has been repeated for over 2000 years. Known not only for looting and robbing, their main source of income has been the capture of humans to be enslaved or held for ransom. Julius Caesar was once captured and ransomed, but returned to crucify his pirate captors. Action against the Barbary pirates was the first military engagement by the U.S. Marines. The offense of piracy including activity in the slave trade after civilized nations outlawed that practice. Indeed the last person hanged in the United States for piracy was captured bringing in Africans during the Civil War. Modern pirates have attacked merchant vessels, holding cargoes and crew for ransom near Africa and in the Caribbean, and causing action in the U.N. Because it is considered an offense against all nations, piracy is covered by the universality principle, authorizing any state to capture, tray, and punish pirates. A new category has recently been added called environmental piracy, also covered by the universality principle.