When South Carolina seceded they commanded that all military property be turned over to the Confederates. When Beauregard and Anderson failed to come to an agreement, the Confederates attacked Fort Sumter. The Union handed it over with no casualties.
First Battle of Bull Run
July 21, 1861
It was the first large-scale battle between the Union and the Confederates. The Confederates were able to defeat the Union and drive them back to DC.
The Union tried to take Richmond from the Confederates. However, Lee was able to defend the city and drive them from the peninsula.
March 9, 1862
Monitor and the Merrimack were the first iron warships. There was no definite winner, but it did end the usage of wooden warships.
Battle of Shiloh
April 6, 1862
The Union attacked the Confederates driving them back. The Confederate then made a surprise counter-attack and were able to drive Union out of their camp before their reinforcements came. However, once the Union received their reinforcements they were able to drive the Confederates from the battlefield.
Battle of Antietam
Lee split his men into four divisions to fight the Union. However, the Union figured out his plan and was able to prepare for it. It ended in a draw.
Battle of Chancellorsville
April 30, 1863
The Union made an attack on the Confederates at Chancellorsville. However, when the Union was attacking they got stuck in a thick wilderness so the Confederates were able to surround them and defeat them. Jackson was also accidentally shot at this battle and would end up dying.
Battle of Vicksburg
May 19, 1863
The Union initially tried attacking Vicksburg but were rebuffed both times. Grant came up with a new plan to surround them and wait them out, eventually, the Confederates surrendered.