Who is Corporal T. J. Doherty from With the Old Breed, at Peleliu and Okinawa and what is their importance?

Doherty is Platoon 984's Drill Instructor during boot camp in November and December, 1943 in San Diego. Doherty's unusually low rank for a Drill Instructor is noted by the men at first, but it in no way compromises his ability to perform his work. He is 5' 10" in height and weighs about 160 pounds. Sledge describes him as muscular, with thin lips, green eyes, and a ruddy complexion. He is fearless, mean, and relentless in the pursuit of his duties. He focuses on harsh exercise and discipline under stressful situations. He prefers to march his platoon in the sand on the beach as this is much more difficult than marching on firm terrain.