Answer: British subjects fought themselves before the Declaration of Independence.
Near Step by Step Explanation: Without using any documents, we can just use background knowledge. What is the definition of a civil war?
A war between the citizens of the same country.
Were the American colonists were citizens of Great Britain like the soldiers they thought?
YES!
The American colonists were British Subjects. They were under control of Great Britain, and they were all citizens of the empire. So they fought against themselves until the Declaration of Independence, were the United States formally made themselves American citizens, not British ones.