Joseph E. Mulcahy's WWI Service Records

I recently ordered the NYS WWI Service Records of all 4 of my great-grandfathers. This will be my next foray into trying to interpret service records, as I attempt to do genealogical research in military records. The military service record for one of my paternal great-grandfathers, Joseph Eugene Mulcahy, consisted of two cards, each pictured here (front and back).

The biographical information in this record substantiates what I already knew. Joseph E. Mulcahy was born 3 September 1896, and lived at 85 Luqueer Street in Brooklyn. According to the record, he enlisted at Fort Slocum, NY on May 9, 1917. I've never been able to find a WWI draft card for Joseph Mulcahy; instead, I have an article from the Brooklyn Daily Standard Union, dated 28 June 1917, describing how he and his brothers enlisted after their father's death.

28 June 1918

This has always lead me to assume that they did not need to register for the draft because they enlisted instead. The Navy Service Record that I received for my other paternal great-grandfather, John O'Hara, has led me to reconsider whether this is accurate, since he seemed to both sign up for the Navy and enlist.

The service record goes on to record Joseph's promotions through the ranks. He was promoted to Corporal on 19 Aug 1917, and to Sergeant on 19 April 1918. The first card says that he accepted a commission on 4 June 1918; the next card says that he was appointed 2nd Lieutenant on 5 June 1918. (Would these two events not have been simultaneous?)

I also received from a cousin a scanned copy of Joseph's promotion to 2nd Lieutenant, which is dated 1 June 1918.

Suffice it to say, by the end of the first week of June, he was a 2nd Lieutenant. At my present level of knowledge, I can't be more precise than that.

Joseph E. Mulcahy's "principal stations" were at Camp Gordon, GA; Camp MacArthur, TX; and Camp Johnston, FL. He received an honorable discharge on 3 Dec 1918, approximately 6 months after receiving his commission, and without ever having been involved in any engagements or even served overseas.