What tactic did ulysses s. grant use successfully against the confederate at petersburg?

Ulysses S. Grant planned and successfully executed a siege attack against the Confederate's army at Petersburg. In the event known as "The Battle of the Crater" as part of the American Civil War, the Union Army of the Potomac, defeated the Confederates under the direct supervision of the general-in-chief, Lt. Gen. Ulysses S. Grant.

not to sure thinking it would be a hope this