The army of the Potomac was the most important union army in the eastern theatre.It originated in the army of the northern Virginia. The army of the Potomac was created in 1861, but was no larger than a corp. But then it grew and became the largest army in the civil war. It was disbanded after 1865 or after the civil war. The main purpose of the Potomac army was to capture the Richmond and to defend the capital Washington D.C. In order to protect the capital and to capture Richmond the Potomac army fought many battles such as Battle of Gettysburg, and the seven days battle. The army of the Potomac used many weapons, such as heavy artillery, no