Read this excerpt from a letter by civil war soldier sullivan ballou:

i have no misgivings about, or lack of confidence in the cause in which i am engaged, and my courage does not halt or falter. i know how strongly american civilization now leans on the triumph of the government and how great a debt we owe to those who went before us through the blood and sufferings of the revolution. and i am willing—perfectly willing—to lay down all my joys in this life, to maintain this government, and to pay that debt.

why is this letter an important primary source document?
it explains the cause of the american revolution.
it explains what he means by american civilization.
it gives insight into what the soldiers believed.
it shows where the key battles occurred.