In the spring and summer of 1918, two young Americans risked their lives to save fellow soldiers from German advances on the French front line during World War I. On Tuesday, President Obama will posthumously award the Medal of Honor to both of them.

During night sentry duty on May 15, 1918, one of the men, Pvt. Henry Johnson of the Army, helped his “Harlem Hellfighters” regiment repel a surprise attack by a dozen German raiders. With only a knife, he singlehandedly held off the enemy, preventing the capture of a wounded fellow soldier.

Private Johnson died about a decade later, a victim of 21 combat-related injuries.