When McClellan heard that there was a smaller force fortifying the area around Yorktown, he turned away from Richmond in favor of taking on the Rebels in that region. Unfortunately for the Confederates, Johnston and most of his army was not on the peninsula when McClellan reached them, leaving Magruder and two small divisions to fight against the Yankees. Fortunately, for Magruder, he used theatrics to persuade McClellan and his troops there was a much larger army occupying Yorktown. McClellan then insisted on building siege fortifications to hopefully take on this supposedly large group of forces.
While the Union batteries were continuously firing upon Yorktown, there was only one that actually fired upon Confederate forces. Johnston, however, always knew that he would have the troops leave Yorktown, and began this procedure on the night of May 3 by ceasing all diverting fire from his heavy guns. The following morning, McClellan and the Union soldiers discovered that Yorktown was deserted by the Confederates, leaving behind weaponry that would aid them in future battles, such as the newly discovered land mines.
Seizing these weapons would prove to be a great benefit to the Union as they would go on to ultimately win the Civil War three years later. At the time of the conflict, there had never been such a humongous amount of artillery used in the world. McClellan eventually left the Yorktown Peninsula in August 1862 leaving behind some units to keep control of Yorktown through the end of the war when Major General Ulysses S. Grant requested that Yorktown be abandoned at the beginning of the siege of Petersburg.