I had found George A Thompson. His unit, company H was a part of the Fifth Regiment of the Massachusetts Volunteer Militia (or MVM for short). Company H was also known as the Salem Guard.
According to his roster, George had enlisted 4/19/1861, a week after Sumter had been fired upon, and was mustered in on May 1 (more things to look up for understanding). And was listed as a casualty 7/21, the Battle of Bull Run (or First Bull Run, so as not to be confused with Second Bull Run).
But there was no Edward T Osgood. Not in company H, nor in any other companies of the Massachusetts Fifth regiment.
Another search finally turned up ET in the 23rd Regiment of Massachusetts Volunteer Infantry (MVI). On their roster he was listed as the fourth sergeant in Company A. But nowhere does it mention that the 23rd was at First Bull Run, in fact the date of his enlistment was given as August 21, 1861, a month after that battle. So, again there seemed to be no connection to Thompson.
As a first step, I looked up a listing for a regimental history of the 23rd, found it, and as my local library did not have a copy, I ordered it from the InterLibraryLoan department.
Meanwhile I could wonder about some of the other clues from this roster entry.
Like exactly what was a “Cordr”?