All day long the Union batteries and the Confederate batteries had been replying to one another. General Fitz John Porter had estimated that the forces under his command were greatly overmatched. Early in the day he had determined upon a battle of resistance, and made up his mind to hold the enemy in check if possible. A long line of infantry that stretched along the swampy bottom-lands and woody ravines were hardly enough to guard and support the artillery which had been placed in positions more or less exposed on the crests of the hills and the vantage spots south of the Chickahominy. This river divided the Union army, making it almost impossible to send re-enforcements to the right wing or to gather it together on the right bank. On June 14 the Confederate General Stuart had made a dashing raid around McClellan's army. The slow-moving infantry had not had time to cut them off. General Porter had posted his batteries of artillery, and had been employed all the morning in forming his lines to await the enemy's attack. General P. St. George Cooke had been instructed to take his position with the small body of cavalry at his disposal under the hills in the valley of the Chickahominy. It was expected of him to support the artillery stationed there and to guard the left flank of the long line. The whole attitude of the Union forces, as we have said, was one of defence. The battle opened on the left in the morning, and by two o'clock in the afternoon had spread along the entire front. It was a strange fact that all of the severe battles of the seven days' fight before Richmond began after noonday. From one o'clock until six Cooke's cavalry, consisting of two and one-half squadrons of the Fifth Cavalry, belonging to the First Brigade; three squadrons of volunteer lancers from Pennsylvania, under Colonel Rush, belonging to the Second Brigade; and two skeleton squadrons of the First United States Cavalry, under Colonel Blake, to which were added the provost-guard under Lieutenant-Colonel Grier--had stood inactive in a sheltered position a little to the rear of the artillery, that had not begun firing until quite late in the afternoon. A few minutes past six General Cooke observed that the infantry on the left wing in front of him was giving way, and at this moment three reserve batteries that had been silent the whole day opened fire upon the enemy advancing through the underbrush at the bottom of the slope. General Cooke ordered the Fifth and First Cavalry to the front, and deployed them a little to the rear of and just filling the intervals of the two right batteries. The Confederates had opened a hot fire of musketry, and shells were falling all about as the men took up their positions. Turning to Captain Whiting of the Fifth, General Cooke said, "Captain, as soon as you see the advance-line of the enemy rising the crest of the hill, charge at once without any further orders, to enable the artillery to bring off their guns."