----
88,500 *

(*2 This estimate is rather larger than that of the Confederate
historians (Allan, W.H. Taylor, etc., etc.), but it has been arrived
at after a careful examination of the strength at different dates and
the losses in the various engagements.)

June 24.

On the night of June 24 the whole of these troops, with the exception
of the Valley army, were south of the Chickahominy, holding the
earthworks which protected Richmond. Less than two miles eastward,
strongly intrenched, lay four of McClellan's army corps, in round
numbers 75,000 officers and men.* (* Return of June 20, O.R. volume
11 part 1 page 238.)

To attack this force, even after Jackson's arrival, was to court
disaster. The right was protected by the Chickahominy, the left
rested on White Oak Swamp, a network of sluggish streams and
impassable swamps, screened everywhere by tangled thickets. It needed
not the presence of the siege ordnance, placed on the most commanding
points within the lines, to make such a position absolutely
impregnable.

North of the Chickahominy, however, the Federals were less favourably
situated. The Fifth Army Corps, 25,000 strong,* (* The Fifth Army
Corps included McCall's division, which had but recently arrived by
water from Fredericksburg. Report of June 20, O.R. volume 11 part 1
page 238.) under General FitzJohn Porter, had been pushed forward,
stretching a hand to McDowell and protecting the railway, in the
direction of Mechanicsville; and although the tributaries of the
Chickahominy, running in from the north, afforded a series of
positions, the right flank of these positions, resting, as Stuart had
ascertained, on no natural obstacle, was open to a turning movement.
Furthermore, in rear of the Fifth Corps, and at an oblique angle to
the front, ran the line of supply, the railway to West Point. If
Porter's right were turned, the Confederates, threatening the
railway, would compel McClellan to detach largely to the north bank
of the Chickahominy in order to recover or protect the line.

On the north bank of the Chickahominy, therefore, Lee's attention had
been for some time fixed. Here was his adversary's weak point, and a
sudden assault on Porter, followed up, if necessary, by an advance
against the railway, would bring McClellan out of his intrenchments,
and force him to fight at a disadvantage. To ensure success, however,
in the attack on Porter it was necessary to concentrate an