Twelfth Corps resting on a small stream at a point where it crossed the Baltimore pike, and which formed, on the right flank of the Twelfth, something of an obstacle. The Cemetery Ridge extended in a westerly and southerly direction, gradually diminishing in elevation until it came to a very prominent ridge called Round Top, running east and west. The Second and Third Corps were directed to occupy the continuation of the Cemetery Ridge on the left of the Eleventh Corps. The Fifth Corps, pending the arrival of the Sixth, was held in reserve. While these dispositions were being mad, the enemy was massing his troops on an exterior ridge, distant from the line occupied by us from 1 mile to 1 1/2 miles. At 2 p. m. the Sixth Corps arrived, after a march of 32 miles, accomplished from 9 p. m. the day previous. On its arrival being reported, I immediately directed the Fifth Corps to move over to our extreme left, and the Sixth to occupy its place as a reserve for the right. About 3 p. m. I rode out to the extreme left, to await the arrival of the Fifth Corps and to post it, when I found that Major-General Sickles, commanding the Third Corps, not fully apprehending the instructions in regard to the position to be occupied, had advanced, or rather was in the act of advancing, his corps some half a mile or three-quarters of a mile in front of the line of the Second Corps, on the prolongation of which it was designed his corps should rest. Having found Major-General Sickles, I was explaining to him that he was too far in advance, and discussing with him the propriety of withdrawing, when the enemy opened on him with several batteries in his front and on his flank, and immediately brought forward columns of infantry and made a most vigorous assault. The Third Corps sustained the shock most heroically. Troops from the Second Corps were immediately sent by Major-General Hancock to cover the right flank of the Third Corps, and soon after the assault commenced the Fifth Corps most fortunately arrived and took position on the left of the Third, Major-General Sykes, commanding, immediately sending a force to occupy the Round Top Ridge, where a most furious contest was maintained, the enemy making desperate but unsuccessful efforts to secure it. Notwithstanding the stubborn resistance of the Third Corps, under Major-General Birney {Major-General Sickles having been wounded early in the action
, the superiority of numbers of the enemy enabling him to outflank the corps in its advanced position, General Birney was compelled to fall back and reform behind the line originally designed to be held. In the meantime, perceiving the great exertions of the enemy, the Sixth Corps, Major-General Sedgwick, and part of the First Corps {to the command of which I had assigned Major-General Newton
, particularly Lockwood's Maryland brigade, *together with detachments from the Second Corps, were all brought up at different periods, and succeeded, together with the gallant resistance of the Fifth Corps, in checking and finally repulsing the assault of the enemy, who retired in confusion and disorder about sunset, and ceased any further efforts on the extreme left. + An assault was, however, made about 8 p. m. on the Eleventh Corps from the left of the town, which

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*See Williams to Slocum, December 26, 1863, p. 765.

+See Meade to Halleck, February 25, 1864, p. 120.

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