At about 1:20 into the opening credits, a Navy ship sails into view from the left. On the bow is a small vertical mast (the jackstaff) flying a small flag (the Jack). The Jack and jackstaff are only used when the ship is anchored or moored never when it is underway.
Throughout the series Marines are heard referring to people as AWOL (Absent Without Leave). This is an Army term. Marines or Sailors would always say UA (Unauthorized Absence).
Although the Marines are correctly shown using Springfield rifles in Guadalcanal, the model shown is the 1903-A3. The Marines actually used the earlier 1903 Model as distinguished by its different rear sight.
By the 1960's the term AWOL was used throughout the U.S. Armed Forces, and while most believe it is an acronym for "Absent Without Leave", it is technically an acronym for "Absent Without Official Leave" (AWOL). Minor point, although one which more should be made aware of.
Lt Col. John A.Butler was the battalion commander of the 1/27 from training till his death on Iwo Jima March 5th 1945
Not LtCol Justin G. Duryea . LtCol Duryea was the interim commander until his injury March 9th 1945