Why was the siege of petersburg important and what was the outcome?

The Siege of Petersburg was important because Lee was pinned down to defend

the fortified system Richmond-Petersburg and the vital railroads and communication lines which fed the Confederate Army of the Northern Virginia and Richmond with its industrial and military factories. Therefore, having lost his freedom of movement he was subjected to Grant's initiative in an endless

war of attrition that was slowly leading to an inevitable collapse of his army, due to its inferior number and equipment, whose losses were getting more and more difficult to replace.

The final loss of the Shenandoah Valley after the annihilation of Early's Confederate army further worsened the situation, making available Sheridan's Cavalry Corps for the set up of a powerful mobile force that was employed to outflank the Rebel defensive line southwest Petersburg and the consequent evacuation of both Richmond and Petersburg by Lee's army, on April 2,1865, after the battle of Five Forks, fought the day before.