Postles received his country's highest award for bravery during combat, the Medal of Honor, for actions taken on July 2, 1863 during the Battle of Gettysburg.

During an attack in the Sunken Road, Company A lost roughly half its men, including its captain.

Following the battle, Postles was lauded by his commanding officer as behaving with "exemplary coolness and bravery", and was named the new Captain for Company A.

[1] Postles also received commendations during the Battle of Gettysburg when he volunteered to ride on horseback to deliver a letter in the face of heavy enemy fire, and returned unharmed.

The President of the United States of America, in the name of Congress, takes pleasure in presenting the Medal of Honor to Captain (Infantry) James Parke Postles, United States Army, for extraordinary heroism on 2 July 1863, while serving with Company A, 1st Delaware Infantry, in action at Gettysburg, Pennsylvania.