Major Montgomery was a native of Dallas, Texas, when he entered the Air Corps. After gaining his wings he was assigned to the 4th Fighter Group, 334th Squadron on 15 May 1943. He remained in that squadron until the end of the war. At the end of his first tour he earned a leave to the states, having destroyed 11 enemy aircraft. His first plane, a P-47 Thunderbolt, was named "Texas". Upon return from his leave he was assigned a P-51 Mustang, which he promptly named " Sizzlin Liz". He soon was named Squadron Operations Officer. He continued to knock out enemy aircraft and eventually had 14.5 to his credit when the war ended.

By the end of January 1944, the 334th had destroyed 48 enemy aircraft. A pool of £30 was collected from from the pilots, to be paid to the one who destroyed the 50th plane for the squadron. On 10 February a support mission was flown to Brunswick, Germany.

An aggressive group of Me-109s and Fw-190s attacked and were engaged by the Group. Three pilots from the 334th squadron (Lt Thomas Biel, Major Gerald Montgomery, and Captain Victor France) each scored one enemy aircraft shot down with no way of determining which one got the 50th. To resolve the situation each of the three received £10.

Two months later Lieutenant Biel was shot down and killed. In March, Captain France, while chasing a 109, hit the ground; his plane exploded and he was killed. Major Montgomery was the only one of the three to have survived the war.

He is believed to have been killed in action during the Korean War. He was listed as Missing In Action until May 2004, when a marker was placed in Arlington National Cemetery with full military honours and a fly-by.

KIA has Deputy Wing Commander 136th FBW while based at Taegu Airfield (K-2) S. Korea. He was flying F-84E s/n 50-1169 when he was shot down by flak over N.Korea on March 3, 1952.