Battle information, July 3
Battle of Mt St Mary
Custer charged down from Mt St Mary against Imboden's cavalry near Emmitsburg, but his attack saw significant tactical errors. Imboden's artillery was ready for him, and his "Wolverines" discovered to their dismay that their Spencer rifles - while effective in a short range firefight - were not able to suppress well placed enemy artillery.
Custer attempted a charge against the artillery line, but was repulsed and then countercharged, ultimately losing half his brigade (1,000 men all told) in killed, wounded and missing and retreating to his position atop Mt St Mary in disarray.
Battle of Monterey
Johnson's division launched a heavy attack against the rearguard of the Union 6th Corps, taking advantage of the rest of the corps departing the position. Newton was forced into a retreat which quickly turned into a rout, a state further promoted by the discovery that their retreat route through Monterey Pass to the west was covered by Confederate cavalry.
Over half the starting strength of the division was killed, wounded or captured (2,500 men in total) and Newton's division ended the retreat on the far slope of South Mountain on the road to Baersville.
Early and Rodes' divisions closed in to envelop the remainder of 6th Corps over the course of the day, and despite Custer's best efforts to prevent this by the middle of the afternoon the whole of Ewell's corps was in position to assault. Meade attempted to pre-empt the coming assault by a breakout to the northeast, but was unsuccessful in doing so before the main Confederate attack took place.
Early's division lost 500 men in the fighting, but the 6th Corps suffered 1,500 casualties in the fighting itself before breaking and routing over McKee's Hill to the northeast. Imboden's cavalry harrassed the retreating Federals but was unable to fully prevent the breakout, with the result that out of 8,000 men involved in the fighting around 3,500 evaded the immediate pursuit, ending two miles northeast of Emmitsburg.
Following this engagement, Lee directed Rodes' division west to pursue Newton's division, and had Heth, Early and Johnson follow up on the rest of 6th Corps.
Early and Johnson caught up with the retreating 6th Corps just as the sun was sinking behind South Mountain to the west, approaching from both directions at once, and Johnson led off with a heavy artillery bombardment down the Emmitsburg Pike before his main attack. The bombardment and attack itself were hastily organized owing to the rapidly dimming light, but 6th Corps was in no shape to organize counter-battery fire; a further 1,000 casualties were inflicted and the integrity of the remainder of the corps badly compromised.
The final fighting for Wright and Howe's sadly depleted formations came by the light of a full moon, as Heth's division of Hill's corps slammed into the bivouac area of the two divisions. Caught by surprise and at the end of their tether, the 2,500 men left between the two divisions surrendered, though Sedgwick was discovered not to be among the prisoners and General Meade was spotted departing by moonlight.
Rodes caught up with Newton's division towards 6:30 PM, and launched a swift attack which captured half the remaining infantry in the division. Now down to the strength of a small brigade, the remaining members of Newton's division (and indeed of 6th Corps by midnight) fled into Franklin County.
Skirmish at the Stone Bridge
After manoeuvering, Robertson attacked Farnsworth's cavalry near Henry House Hill. The attack was partially successful, forcing Farnsworth into a retreat to Manassas Junction, but no significant casualties were suffered on either side.
The state of the Army of the Potomac has led to an automatic Confederate victory.
2 divisions destroyed THIS TURN, +6
1 cavalry brigade destroyed LAST TURN, +1
Routed divisions:
Newton (D2), +2
in 6th Corps +1
Ayres, Barnes (D1) +2
In 5th Corps +1
42 casualties to AoP (21,000 men), +5
Total 18
Union FLIGHT (14+) = automatic victory
In addition, the Confederates are currently on 248 victory points. If the game continued and the Union army recovered down to not being in DISORDER they would lose 25 of those victory points, bringing them down to 223; 230 is the requirement for a decisive victory by victory points.
It's up to both sides if they want to continue to see what happens now, but if not here's my write-up:
The Pennsylvania Campaign
Lee's invasion of the north began when his army marched west from positions along the Rappahannock on June 3. Hooker followed him towards and into the Shenandoah, and the following two-three weeks saw wet, miserable weather as the armies manoeuvred for position in the Shenandoah Valley area and Lee's forces systematically destroyed most of the Union garrison forces in the area.
The Confederate army began crossing the Potomac around the 22nd June, marching up the Cumberland Valley and aided in their movements by another series of freshets preventing the crossing of the Potomac at the fords. Hooker ultimately had his 5th, 6th and 3rd Corps cross the Potomac in the area of Berlin Ferry, his 1st and 2nd Corps at Harpers Ferry and his 11th and 12th Corps cross near Williamsport, with almost the entirety of his cavalry (and the 3rd Corps) joining 1st, 2nd, 11th and 12th in the Cumberland Valley area.
Lee employed his own cavalry more judiciously, splitting it between the two sides of South Mountain, and made good use of the Chambersburg Pike to cross most of two of his corps (Hill's and Ewell's) into York County at a time when only two Union corps were east of South Mountain; at the same time, Anderson raised havoc in Cumberland County before marching rapidly south to join in.
Lee's Old War-Horse Longstreet managed the three divisions left available to him, along with around two thirds of the army's cavalry, to keep no fewer than five Union corps and nearly every cavalryman in the army occupied and off balance.
Hooker meanwhile was suffering from intense pressure from Washington to produce some kind of victory - any victory - and pushed his forces hard enough that widespread supply problems broke out in his army. This was enough that the pressures against him finally became insurmountable.
At the beginning of July, Hooker was replaced by Meade. The attendant command confusion of this switch was exactly what Lee was waiting for, however, and he pounced with a sequence of attacks on July 2-3 ultimately involving five divisions east of South Mountain - first knocking back 5th Corps with a devastating two-pronged attack, then surrounding and effectively destroying the Union 6th Corps. Estimates are that this two-day period knocked a total of 19,000 men off the Army of the Potomac's order of battle.
The morale impact of this on the Union was extreme, as the "Battle of Westminster Pike" (or Battle of Monterey) could not be presented as anything other than an unambiguous Confederate victory on northern soil.
In this case, there were three key Union errors which I think contributed significantly to the outcome. Two of them are "strategic", and the other is "tactical".
The first strategic error was to concentrate 1st, 2nd, 3rd, 11th and 12th and most of the cavalry into the Cumberland Valley. This led to a situation where there were about 55,000 or so men west of South Mountain and only about 25,000 men east of it, at a time when Lee had control of the passes leading through South Mountain, while the Union had insufficient scouting assets checking on Lee's force distribution.
The second strategic error was in pushing the Union army so hard that most of the force ran out of supply. This led to a situation where most of the army was weakened (from being out of supply) and static (to forage).
The third, more tactical error was in putting 6th Corps into the Monterey area and 5th Corps into Emmitsburg, rather than having the two of them more mutually supporting in open country (and closer together). It meant it was easy to trap them and deal with them in succession.