In July, he was put in command of the "Provisional Brigade," and joined the army of the Shenandoah, of which in August General Sheridan took command. He was so struck with Lowell's work during the next month that in September he put him in command of the "Reserved Brigade," a very fine body of cavalry and artillery. In the fierce and continuous fighting that ensued Lowell was everywhere conspicuous, and in thirteen weeks he had as many horses shot under him. But he now had scope to show more than the dashing gallantry which distinguished him always and everywhere. His genuine military ability, which surely would have led him to the front rank of soldiers had his life been spared, his knowledge, vigilance, and nerve all now became apparent. One brilliant action succeeded another, but the end was drawing near. It came at last on the famous day of Cedar Creek, when Sheridan rode down from Winchester and saved the battle. Lowell had advanced early in the morning on the right, and his attack prevented the disaster on that wing which fell upon the surprised army. He then moved to cover the retreat, and around to the extreme left, where he held his position near Middletown against repeated assaults. Early in the day his last horse was shot under him, and a little later, in a charge at one o'clock, he was struck in the right breast by a spent ball, which embedded itself in the muscles of the chest. Voice and strength left him. "It is only my poor lung," he announced, as they urged him to go to the rear; "you would not have me leave the field without having shed blood." As a matter of fact, the "poor" lung had collapsed, and there was an internal hemorrhage. He lay thus, under a rude shelter, for an hour and a half, and then came the order to advance along the whole line, the victorious advance of Sheridan and the rallied army. Lowell was helped to his saddle. "I feel well now," he whispered, and, giving his orders through one of his staff, had his brigade ready first. Leading the great charge, he dashed forward, and, just when the fight was hottest, a sudden cry went up: "The colonel is hit!" He fell from the saddle, struck in the neck by a ball which severed the spine, and was borne by his officers to a house in the village, where, clear in mind and calm in spirit, he died a few hours afterward.