By nightfall of the first, both armies were in state of readiness for the conflict. The Union army was on the defensive. It was sufficient that it should hold its ground and repel all assault. The Confederates must advance and carry the Federal position in order to succeed. How this should be done was not agreed on by the Confederate commanders. General Lee formed a plan of direct assault; but General Longstreet was of opinion that a movement of the army to the Union left flank would be preferable, and that by that method the flank might be turned and the position of Meade carried with less loss and much less hazard.
Longstreet, however, did not oppose the views of his commander to the extent of thwarting his purpose or weakening the plan adopted. On the second of July the battle began in earnest about noon. The Confederates advanced against the Union centre and left, and at a later hour a strenuous and partly successful attack was made on the Federal right. But complete success was not attained by Lee in any part of the field. About sundown the Confederates gained considerable advantage against Slocum, who held the line along Wolf Hill and Rock Creek; and on the Union left a terrible struggle occurred for the possession of Great and Little Round Top. In this part of the field the fighting continued until six o'clock in the evening; but the critical positions still remained in the hands of the Federals.
In the centre the contest was waged for the mastery of Cemetery Hill, which was the key to the Union position. Here were planted batteries with an aggregate of eighty guns, and here, though the assaults of the Confederates were desperate and long continued, the integrity of the Federal line was preserved till nightfall. The fighting along a front of nearly five miles in extent continued in a desultory manner until about ten o'clock on the July night, when the firing for the most part ceased, leaving the two armies in virtually the same position which they had occupied the day before.
This signified, however, that thus far the advantage was on the Union side; for on that side the battle was defensive. The Confederate army had come to a wall, and must break through or suffer defeat. The burden of attack rested on the Confederate side; but General Lee did not flinch from the necessity. In the darkness of night both he and the Union commanders made strenuous preparations for the renewal of the struggle on the morrow.