I didn’t see your Comment until after I posted.
My Dad was an Army radar specialist who went in D+1.
Please check out my Comment #27.
I have no idea what unit my Father was attached to, but he and his lieutenant and squad were bunked all alone with Marines on their transport ship.
Is it possible radar guys were in Army Signals, too?
Re “Is it possible radar guys were in Army Signals, too?”
I would say yes based on what I’ve read in the official military histories of WW2 in the “Green Books”.
Radar specialists were in the Signal Corps (see if your father graduated from Ft. Monmouth, NJ SC school). They set up anti-aircraft radar units all over the Pacific, esp. where the Japs had airfields or carrier task forces.
Also used to pick up incoming US bombers and fighters who needed guidance to emergency bases, esp. on Iwo Jima.
My father-in-law was in an Assault Wave while others came in, possibly like your father, as detached elements to the Marines. Or perhaps your father was in an Assault Wave but after the beaches and shorefronts had been secured. Signal Corps men were not trained to be frontline assault troops but did fight when necessary.
They were electronics specialists - radio communications, radar, Forward Observers who called in target positions to both ships and land artillery, etc. They were the communications lifeline people for the Marines.
Very brave men.