Semmes' brigade had followed close behind Kershaw's, and now took its place. Its commander speedily fell, mortally wounded. Barksdale rushed upon Graham, followed by Wofford. This onset brought the whole Confederate force into action. The odds were as two to one. That part of the enemy whom we left working their way up the hollow to Little Round Top also met with stubborn resistance, and as this was more and more seen to be the critical point, the enemy redoubled their efforts to force their way through. Our soldiers who had gone into ambuscade behind the bowlders there were being gradually driven back from cover to cover, so yielding up as they retired the approaches to Little Round Top. [Sidenote: Devil's Den taken.] Having gained this vantage-ground the Confederates now made a second onset against Ward and De Trobriand. This time it proved more successful. After an hour's obstinate fighting, Ward was driven out of his fastness,[66] De Trobriand forced back across the wheat-field. Sickles' left was thus completely broken up, the fragments drifting backward in search of some point of support. [Sidenote: Little Round Top in Peril.] Little Round Top was about to fall into the enemy's hands. Once in his possession, the Union line on Cemetery Ridge would have to be abandoned or swept to the winds. Fortunately the turning-point had been reached before the rebels could reap the reward of Ward's repulse. Shortly before Hood's onset began, General Warren, of the Engineers, had seen from his signal-station on Little Round Top the enemy's line advancing to the attack. In one moment his experienced eye took in all the danger. Ordering the signal officers to keep on waving their flags, Warren first sent for and then dashed off in search of assistance himself. Indeed, not a moment was to be lost. By a fortunate chance some troops were met moving out to reinforce Sickles. Detaching a regiment, Warren hurried it off to the threatened point. Meantime, in response to his request, though without his knowing it, Vincent's brigade was climbing the rearmost slopes off Little Round Top, arriving just in time to save the hill with the bayonet.[67]