A century and a half after his valiant death in the Battle of Gettysburg, a Union Army officer is being awarded the nation’s highest military decoration, thanks to a decades-long campaign by his descendants and Civil War buffs.

The White House announced Tuesday that President Barack Obama approved the Medal of Honor for 1st Lt. Alonzo H. Cushing, who was killed standing his ground against Pickett’s Charge during the pivotal, three-day Battle of Gettysburg.

Congress granted a special exemption last December for Cushing to receive the award posthumously since recommendations normally have to be made within two years of the act of heroism and the medal awarded within three years.

The White House also announced that Obama will award the medal in a ceremony on Sept. 15 to two Vietnam War soldiers who also received the congressional exemption — Army Command Sgt. Maj. Bennie G. Adkins and Army Spc. Donald P. Sloat. The medal is given to members of the Armed Forces who risk their own lives in acts of great personal bravery.

Cushing was born in Delafield, Wisconsin, raised in Fredonia, New York, and buried at his alma mater, West Point, after being killed on July 3, 1863, at age 22. He commanded about 110 men and six cannons, defending the Union position on Cemetery Ridge against Pickett’s Charge, a major Confederate thrust that could have turned the tide in the war. Cushing received a bullet wound in the head.

The fierce battle near the town of Gettysburg, Pennsylvania, resulted in more than 51,000 casualties. Confederate soldiers advanced into the Union fire but eventually retreated with massive losses. The South never recovered from the defeat. Four months later, President Abraham Lincoln memorialized the Union war dead in his Gettysburg Address.