That reminds me, just thought of it - my dad was in WWI - he was a COOK! He raised two pigs every year and we had chickens and fruit trees - figs and peaches. Slaughtered those pigs, salted the meat, plus made sausage and it was stored in his smoke house. He also barbecued meat.
Could cook anything - we actually had squirrel and frog legs he caught. We never lacked for meat and he could cook it.
Back in those days, don't know if cooking schools were around so one could be a chef. He would probably have laughed at that, but the man could cook.
The Union military had some sanitation/logistics/food training during the Civil War, but many troops cooked in small groups like Rome's legions 2000 years before.
Health advances led to better training of military cooks before the 1st WW. By your dad's time, he probably had good training, and lots of experience.
I went through the military school, and then went to a civilian school. If I was in uniform, proper form of address was Sgt or TSgt, if in a civilian jacket, the appropriate term of address was el jefe de cocina, or Chef. ;)
/johnny