What parts of the letter explained what side Sullivan ballou was on?

hope this is helpful in the picture below

Sullivan Ballou (March 28, 1829 – July 29, 1861) was a lawyer and politician from Rhode Island, and an officer in the Union Army during the American Civil War. He is remembered for an eloquent letter he wrote to his wife Sarah, one week before he was killed in the First Battle of Bull Run.

buildings

explanation:

answer; they are called (pebbling);