After weeks of preparation, on July 30 the Federals exploded a mine in Burnside's IX Corps sector beneath Pegram's Salient, blowing a gap in the Confederate defenses of Petersburg. From this propitious beginning, everything deteriorated rapidly for the Union attackers. Unit after unit charged into and around the crater, where soldiers milled in confusion. The Confederates quickly recovered and launched several counterattacks led by Maj. Gen. William Mahone. The break was sealed off, and the Federals were repulsed with severe casualties. Ferrarro's division of black soldiers was badly mauled. This may have been Grant's best chance to end the Siege of Petersburg. Instead, the soldiers settled in for another eight months of trench warfare. Maj. Gen. Ambrose E. Burnside was relieved of command for his role in the debacle.