A reader came to my rescue with an explanation of the stamp in September, and I've just gotten around to exploring the reader's comment in more detail.
It's somewhat noteworthy when Babe takes the time to comment forcefully about current events.
We know that the 168th Infantry Regiment, 34th Infantry Division, came ashore in Salerno, just south of Naples (and nearly 170 miles south of Rome), in September 1943.
In the return address, Babe had crossed out the "Pvt." in front of his name and written in "T/5."
"It is so essential to morale that army and navy officers of the highest rank list mail almost on a level with munitions and food."