* First tank: Mark I (British, 1915), saw action at Battle of the Somme: Sept. 15, 1916
* French tank: Schneider CA1: Used in collaboration w/ British tanks in Battle of Cambrai: Nov. 20. 1917- first successful mass tank attack.
* Germans did not develop tanks extensively, but did create armor-piercing bullets to counter them.
* Late in the war, the Allies refined their tanks and gave them a rhomboid shape, more armor to deflect German bullets.