The Battle of Gains' Mill

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Due to reports of the advancement of all of Jackson’s force on the Union’s
unprotected flank, Union forces started to withdraw from the Mechanicsville
area early in the morning. The Fourth US, after returning to camp from the
prior nights bivouac collected their knapsacks, sent the sick across the
Chickahominy, and destroyed commissary and other stores (keeping cigars
taken from the sutler’s store). The First brigade crossed the Chickahominy
at Gains’ Mill and took up new positions. The First Brigade was on the
extreme right of the Union forces with the Fourth US at the extreme right of
the brigade’s position. The Fourth US was placed specifically in support of
Weed’s artillery battery which commanded the approach from Old Cold
Harbor. The Second division was originally positioned near New Cold Harbor,
but was later moved to a second position at Dispatch Station on the
Richmond and New York River Railroad. The Third was along the road and
the Twelfth and Fourteenth regiments were in positions in a corn field. The
brigade of General Seymour was the rear guard. While the position was a
strong one, being on the crest of a hill with partial cover from fences, there
was thick timber about 400 yards to the front which masked Confederate movements.

The position occupied by the Fourth US was heavily attacked by Confederate artillery between 11 a.m. and
noon. The position was reinforced by a battery of horse artillery, commanded by Tidball in the early afternoon.
Confederate artillery fire continued, with some breaks until dark. The Confederate troops under D. H. Hill (part
of Thomas Jackson’s Corps) launched three attacks against the batteries protected by the Fourth but, in all
cases were repulsed. At dusk, the batteries, nearly out of ammunition, retired (in his report on the battle,
Captain Weed reports having fired something over 1,000 rounds). Captain Collins, having taken command with
the absence of Major D. Davidson, placed (under fire) the Regiment, by a flank movement, at the double time,
along a split rail fence between the batteries and the Confederate forces, allowing the batteries to retire in
good order. He later followed, also in good order. The Regiment and the batteries bivouacked on the north side
(enemy side) of the Chickahominy, having no orders to cross the river (three messengers, bearing messages
to retire across the river having failed to reach the Regiment). This position covered Grapevine Bridge. The
fierce defense put up by the Fourth US and the two batteries prevented the Confederate forces from turning the
right flank of the Union forces.

Captain Collins retained command of the regiment through the remainder of the seven days fight.

On the morning of the 28th, with the grapevine bridge having been partially destroyed, the regiment at first
started an advance to a point near their prior days’ position but finding that they were the only Union force north
of the river, retired, marched to Alexander’s Bridge and crossed the Chickahominy River at that point – the last
regiment to do so.

The brunt of the fighting at Gaines Mill was done by General Porter’s Fifth Army Corps (1 of 5 Corps in the Army
of the Potomac), the remainder of the Army of the Potomac was in defensive positions south of the Chickahominy.
Against the Fifth Corps, with almost a two to one numerical advantage, were the combined Confederate troops
under Generals Robert E. Lee, James Longstreet, Thomas Jackson, D. H. Hill, and A. P. Hill. Their battle reports
sustained the belief that they had encountered the main body of the Union Army.