Great studio photograph RPPC of a US army soldier from the early 40s. I asked the internet for some help on this one, here's what I found out:
The "T" shoulder patch is that of the US Army Technician 5th Grade rank, in use 1942-1955 (rank instated 1942, discontinued in 1955)
He was in the Army, with the rank "Technician 5th Grade". He also has 2.5+ years "overseas service" hash marks on his lower sleeve.
Top patch is US army Pacific Command