Rock

Sergeant Rock is a sergeant in the U.S. Army who served during World War II.

Biography
Rock served in the army in World War II in Saint-Lô, France. He ran in to Kendra Saunders, who was running away from Vandal Savage. He gave her a pen and paper to write with, before allowing her to stuff it in to his helmet. He was promptly stabbed with a knife by Savage, killing him. His helmet eventually entered the possession of Rip Hunter aboard The Waverider.

Behind the scenes

 * Although not named during his appearance, his helmet was identified via DC Comics' official Instagram.
 * In the DC Comics, Sgt. Frank Rock was an American army officer and leader of the infamous Easy Company unit.