The officer commanding the Union force (which also included cavalry) was Major General William F. "Baldy" Smith, who was somewhat of a martinet. Smith and some of his men had been temporarily transferred to the Army of the Potomac in early June and saw service at Cold Harbor. There, on June 3, he had seen firsthand the folly of attacking well manned earthworks. Because of that experience, his march to Petersburg from Bermuda Hundred and City Point was very slow, and very cautious. Ironically, his combind force of approximately 15,000 men faced only 2,000 Confederates defending Petersburg, but they were posted behind the forbidding Dimmock fortifications.
Smith's advance was stalled for several hours by a stubborn Rebel opposition at an outlying post on Baylor's Farm. Once that was cleared, he spent more time scouting the enemy lines and refining his plans. When he informed his officers that he intended to attack at 4:00 p.m., he learned that his artillery chief, assuming there would be no further action for this late in the day, had sent all his horses to the rear to be watered. It wasn't until 7:00 p.m., thirteen hours after he first made contact at Baylor's Farm, that Smith's assault began.
Smith had correctly guessed the Confederates critical lack of manpower, so instead of attacking en masse, he chose a more dispersed skirmishing formation that provided few targets to the Rebel gunners.
White troops from Colonel Louis Bell's brigade overran Battery 5 on the Dimmock Line, while others surrounded neighboring Battery 6. "Here we had to fight hard," wrote one New York soldier.
Some of the troops in Brigadier General Edward W. Hink's all-black division assisted in capturing Battery 6, while others from that unit rolled the line up to the south, taking possession of Batteries 7, 8, 9, 10, and 11. Rebel batteries 3 and 4 also changed hands. In his brilliant assault, "Baldy" Smith's men had captured more than a mile of the Dimmock Line. Confederate General P.G.T. Beauregard later admitted, "Petersburg at that hour was clearly at the mercy of the Federal commander."
But Smith was feeling anything but sanguine, "I....knew that Confederate reinforcements had been rushing in to Petersburg," he reported. "I knew nothing of the country in front. My troops were exhausted." He decided to risk no more and ordered his men to hold their ground.
For the soldiers who had seen the Rebels flee and who now stood within sight of Petersburg, it was an unbelievable decision. "I swore all night," one of them recalled. "I kicked and condemned every general there was in the army for the blunder I saw them making."
Major General William F."Baldy" Smith