A trader works on the floor of the New York Stock Exchange on August 11, 2011. US stocks made another dramatic comeback after a stunning fall on Thursday, in another day of extreme volatility in markets around the world.
Stan Honda/AFP/Getty Images
Only the U.S. and Britain had fully mechanized militaries, historian Tim Francis says. Most other European allies used horses or donkeys to help move supplies. Or, as in the North, reindeer.