What was the purpose of the siege of petersburg?

Answer 1

The purpose was that of keep Lee pinned down to defend the defensive system Richmond-Petersburg, depriving him of his freedom of movement and managing to make his army collapse.

The goal was reached as follows:

1 - by starting a war of position characterized by a slow, slight but continuous lengthening of the entrenchments south and then westward:

the Northerners attempting to outflank the enemy defense system and aiming to interrupt the vital railroads securing the flux of supply, indispensable to maintain the Confederates' war effort;

the Southerners managing to stop the menace, extending their net of entrenchments.

Every prolongation of the entrenchment was marked by violent fighting or local battles which cost heavy casualties to both sides, with but no decisive outcome.

2 - It was also a war of attrition consciously carried forward by Grant, regardless of how heavy the losses of men and materials could be.

Indeed that was the right way to go to annihilate Lee's Army, because the Union casualties, though generally higher than those of the Confederates who mainly fought on the defensive, were much easier to replace than Lee's.

This situation was getting worse after Sherman's "March to the Sea" had been carried out, interrupting the reinforcements from the Carolinas, and led to the collapse of the Army of the Northern Virginia.

On April 2, 1865, Lee was forced to evacuate Richmond and, in the following day, Petersburg, whose siege was over after about nine months of bloody struggle.