The Confederates evacuated Yorktown on May 3, 1862. The II Union Corps occupied Yorktown on May 4th and then went to the pursuit of the retreating Magruder's army.
During the Peninsula campaign headed by Union General George B. McClellan, he for some unknown reason decided to lay siege to Confederate troops in Yorktown. On May 3, 1862, commanding Confederate General Joseph Johnston decided to evacuate his troops at Yorktown.
Shortly after landing at Fort Monroe in early on May 1st, as the first step in Union General George B. McClellan's so-called Peninsula campaign, he became aware of Confederate forces holding on to Yorktown. It was a small defending force led by Major General John B. Magruder. McClellan decided to lay siege to Yorktown although it seemed he could have easily over run the small force there. Confederate General Joseph Johnston joined forces with Magruder there but then decided to evacuate the area on May 3, 1862.
On May 3, 1862, Confederate forces evacuate Yorktown before Union troops overwhelm them. They have delayed McClellan's advance to Richmond by one month. On May 4, Union troops enter the vacated town.
Two battle had been fought at Yorktown. The first one took place from Oct.6 through Oct. 19, 1781, during the Revolutionary War. The British were decisively defeated and surrendered. The second one took place in 1862. On Apr. 4, McClellan started his offensive along the Peninsula. Finding his way blocked by the Confederate at Yorktown, he decided to lay a regular siege, although his Army of the Potomac overwhelmed 4 to 1 the Confederates. On May 1, the Federals opened fire against the enemy entrenchments, forcing the Confederates to evacuate their positions two nights later and retreat towards Richmond. Yorktown was occupied on May 4.
The Confederate capital, Richmond was captured after the Battle of Five Forks, which forced Lee to evacuate it and Petersburg as well.
Confederate General Albert S. Johnston had little choice but evacuate Nashville in 1862, His force only numbered 11,000 troops and the opposing Union army under General Buell had 40,000 troops.
US General William Sherman learned of the new commander of the Southern Army of Tennessee, John Hood and expected a tough campaign on his way to Atlanta. Despite Sherman's good judgment, he met little resistance from Confederate forces. As the end of July, 1864 approached, he gave thought that the Confederate forces were to evacuate Atlanta without a fight.
Halleck came to the conclusion that even if McClellan did, his planned turning movement would result in becoming an exterior line of operation to General Lee's advantage. Confederate General Robert E. Lee was situated between the armies of Pope and McClellan and could thus form a concentration against either army and result in a major Union defeat. The exterior line situation that the Union had created was a potential disaster. The best move was to evacuate the Peninsula and join Pope in Northern Virginia.
Losing the battle was a big screw up for Britain. The battle at Yorktown was the last and final battle of the 6-year Revolutionary war. Major quarrels in the colonies were over, but British troops still held a few American cities, and at year-end, Parliament had British troops completely let go of America.
The inhabitant of Atlanta were forced to evacuate the city and sheltered behind the Confederate lines.
A series of military events which included Union general Sheridan to overcome the South's position in Five Forks Virginia. With Sheridan's success, General Grant attacked Petersburg, a Confederate city that laid between it and Richmond. Confederate entrenchments which had protected Richmond during the course of the war, no longer had enough soldiers to man the defences. Thus Grant had a clear path to Richmond. News of all these battles reached Richmond in time for the top Confederate leaders to escape.
To join forces with General Joseph E. Johnston in North Carolina. Sheridan headed him off.