The Battle of Yorktown or Siege of Yorktown is fought from April 5 to May 4, 1862, as part of the Peninsula Campaign of the American Civil War.

Marching from Fort Monroe, Union Maj. Gen. George B. McClellan's Army of the Potomac encounters Maj. Gen. John B. Magruder's small Confederate force at Yorktown behind the Warwick Line.

McClellan suspends his march up the Peninsula toward Richmond and settles in for siege operations.

On April 5, the IV Corps of Brig. Gen. Erasmus D. Keyes makes initial contact with Confederate defensive works at Lee's Mill, an area McClellan expects to move through without resistance.

Magruder's ostentatious movement of troops back and forth persuades the Union that his works are strongly held.

As the two armies fight an artillery duel, reconnaissance indicates to Keyes the strength and breadth of the Confederate fortifications, and he advisesMcClellan against assaulting them.

McClellan orders the construction of siege fortifications and brings his heavy siege guns to the front.

In the meantime, Gen. Joseph E. Johnston brings reinforcements for Magruder.

On April 16, Union forces probe a point in the Confederate line at Dam No. 1.

The Union fails to exploit the initial success of this attack, however.

This lost opportunity holds up McClellan for two additional weeks while he tries to convince the U.S. Navy to bypass the Confederates' big guns at Yorktown and Gloucester Point and ascend the York River to West Point and outflank the Warwick Line.

McClellan plans a massive bombardment for dawn on May 5, but the Confederate army slips away during the night of May 3 toward Williamsburg.

The battle takes place near the site of the 1781 Siege of Yorktown.