Bob was promoted to Lieutenant Commander in early March 1943 while still in the South pacific, after which he was flown back to the States to recuperate from the jungle fever he had contracted, leaving him more than twenty pounds lighter.
Lieutenant Commander Montgomery contributed to the ongoing development of dronettes for Navy use. Dronettes had been developed by another actor, Reginald Denny, whose hobby had been radio-controlled model planes.
In February 1944, now 41 and known in the Navy as an outstanding officer, storyteller, and mimic, Bob joined the staff of Commander Destroyer Squadron 6 on the USS Barton. The Barton was one of the hundreds of Allied vessels that were preparing for Operation Overlord, the Normandy invasion. Bob was awarded the Bronze Star for "his cool and courageous performance of duty in the face of frequent devastating enemy aerial attacks throughout the entire assault period."
Yeah, I could literally write out the entire chapter on Bob, but I'll leave it here. As you can see, he did more than his part to serve the country in WWII.
Above from Stars in Blue: Movie Actors in America's Sea Service by Wise & Rehill