Your father-in-law would not have been able to serve with the 744th in 1941, as the designation of 744th AAA Gun Battalion was adopted in 1943. Before this year, all battalions that were designated AAA Gun Battalions were the 1st Battalion of a Coast Artillery (Anti Aircraft) regiment. For instance, the 762nd AAA Gun Battalion, created September 1943, was created from and after the inactivation of 1st Battalion, 72nd CA (AA) regiment. The 891st AAA Gun Battalion was 1st Battalion, 615th CA (AA). 765th AAA Gun Battalion was 1st Battalion, 73rd CA (AA).
If you want to get the record of the 744th AAA Gun Bn, write to: National Archives at College Park 8601 Adelphi Road College Park, MD 20740-6001
That is where I got the copy of the history of my father's unit, the 762nd AAA Gun Battalion, and the 891st AAA Gun Battalion. The name of the regiment your father served would be listed in the history.