McClellan’s difficulties had not escaped the observation of his watchful adversaries, and on the morning of May 31 the Federal lines were heavily attacked by Johnston.  The left of the position on the south side of the Chickahominy was protected by the White Oak Swamp, a broad and almost impassable morass; but the right, thrown back to the river, was unprotected by intrenchments, and thinly manned.  The defence of the first line had been assigned to one corps only; the second was five miles in rear.  The assailants should have won an easy triumph.  But if McClellan had shown but little skill in the distribution of his troops on the defensive, the Confederate arrangements for attack were even more at fault.  The country between Richmond and the Chickahominy is level and well wooded.  It was intersected by several roads, three of which led directly to the enemy’s position.  But the roads were bad, and a tremendous rain-storm, which broke on the night of the 30th, transformed the fields into tracts of greasy mud, and rendered the passage of artillery difficult.  The natural obstacles, however, were not the chief.

The force detailed for the attack amounted to 40,000 men, or twenty-three brigades.  The Federal works were but five miles from Richmond, and the Confederates were ordered to advance at dawn.  But it was the first time that an offensive movement on so large a scale had been attempted; the woods and swamps made supervision difficult, and the staff proved unequal to the task of ensuring co-operation.  The orders for attack were badly framed.  The subordinate generals did not clearly comprehend what was expected from them.  There were misunderstandings as to the roads to be followed, and as to who was to command the wings.  The columns crossed, and half the day was wasted in getting into position.  It was not till 1 P.M. that the first gun was fired, and not till 4 P.M. that the commanding general, stationed with the left wing, was made acquainted with the progress of his right and centre.  When it was at last delivered, the attack was piecemeal; and although successful in driving the enemy from his intrenchments, it failed to drive him from the field.  The Federals fell back to a second line of earthworks, and were strongly reinforced from beyond the river.  During the battle Johnston himself was severely wounded, and the command devolved on General G.W.  Smith.  Orders were issued that the attack should be renewed next morning; but for reasons which have never been satisfactorily explained, only five of the twenty-three brigades were actively engaged, and the battle of Seven Pines ended with the unmolested retreat of the Confederates.  Smith fell sick, and General Lee was ordered by the President to take command of the army in the field.