On Sept. 29, 1872, Sgt. William Wilson won his second Medal of Honor in six months of combat against the Comanches. One of less than two dozen fighting men to receive a pair of American’s highest military decoration, the obscure cavalryman earned both on the battlefields of Texas.

In its 157-year history, the coveted citation had been bestowed upon better than 5,000 servicemen, but only 19 had been so honored on two different occasions. Seven marines, seven sailors and five soldiers compris...