What tactic did Ulysses S. Grant use successfully against the Confederates at Petersburg?

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

d.he wanted to send diplomats to communist countries.