I have been trying to figure out why the Nov-Dec 1941 photos have US Troops with beards. I started reading Lt Ramsey's War and there was the answer. When the families were ordered out of the Philippines, many soldiers vowed to not shave, until they were reunited with thier families. He states that most of the officers of the 26th had beards during the summer of 41.
I remember that too. Also, in the novel Guerrilla and the Hostage, a book by Col. John Olson who was an officer in the 57th Infantry. One reason for beards that he mentioned in the book was that it impressed the Filipinos (who were naturally not hairy and found it difficult to grow beards).
Its one of those myths about the "old army"that has never been confirmed by photos. I think once war with japan seemed unavoidable the beards would have been banned. Japan was a serious threat and the use of gas seemed likely at the time,a beard will affect the fit of the gasmask. Other thing worth mentioning is that hair plus bloody wounds in the tropics is a real bad mix. Somewhere in all my ww2 junk i have a picture of Clinton Pierce departing the States (to take command of the 26th cavalry Regiment)with a beard. The only photo i have of Pierce after the invasion show him clean shaven.