Original sentence: Seven states declared their independence from the United States before Abraham Lincoln was inaugurated as president; four more did so after the American Civil War began with the Battle of Fort Sumter when the CSA attacked the USA
Edited sentence: Seven states declared their independence from the United States before Abraham Lincoln was inaugurated as president; four more did so after the American Civil War began with the Battle of Fort Sumter when the CSA drove the US Forces from the Fort, before it could be reenforced with additional troops, weapons and supplies