Battle of Beaver Dam Creek

The Battle of Beaver Dam Creek, also known as the Battle of Mechanicsville or Ellerson's Mill, took place on June 26, 1862, in Hanover County, Virginia, as the first major engagement of the Seven Days Battles during the Peninsula Campaign of the American Civil War. It was the start of Confederate General Robert E. Lee's counter-offensive against the Union Army of the Potomac, under Maj. Gen. George B. McClellan, which threatened the Confederate capital of Richmond. Lee attempted to turn the Union right flank, north of the Chickahominy River, with troops under Maj. Gen. Thomas J. "Stonewall" Jackson, but Jackson failed to arrive on time. Instead, Maj. Gen. A.P. Hill threw his division, reinforced by one of Maj. Gen. D.H. Hill's brigades, into a series of futile assaults against Brig. Gen. Fitz John Porter's V Corps, which occupied defensive works behind Beaver Dam Creek. Confederate attacks were driven back with heavy casualties. Porter withdrew his corps safely to Gaines Mill.

Background and Lee's plan
After the Battle of Seven Pines, on May 31 and June 1, McClellan and the Army of the Potomac sat passively at the outskirts of Richmond for almost a month. Lee, newly appointed commander of the Confederate Army of Northern Virginia, devoted this period to reorganizing his army and preparing a counter-attack. He also sent for reinforcements. Stonewall Jackson arrived on June 25 from the Shenandoah Valley following his successful Valley Campaign. He brought four divisions: his own, now commanded by Brig. Gen. Charles S. Winder, and those of Maj. Gen. Richard S. Ewell, Brig. Gen. William H. C. Whiting, and Maj. Gen. D.H. Hill

The Union Army straddled the rain-swollen Chickahominy River. Four of the Army's five corps were arrayed in a semicircular line south of the river. The V Corps under Brig. Gen. Porter was north of the river near Mechanicsville in an L-shaped line running north-south behind Beaver Dam Creek and southeast along the Chickahominy. Lee moved most of his army north of the Chickahominy to attack the Union north flank. He left only two divisions (under Maj. Gens. Benjamin Huger and John B. Magruder) to face the Union main body. This concentrated about 65,000 troops against 30,000, leaving only 25,000 to protect Richmond against the other 60,000 men of the Union army. It was a risky plan that required careful execution, but Lee knew that he could not win in a battle of attrition or siege against the Union army. The Confederate cavalry under Brig. Gen. J.E.B. Stuart had reconnoitered Porter's right flank as part of a daring, circumnavigation of the entire Union army from June 12 to June 15 and found it vulnerable. Stuart's forces burned a couple of Union supply ships and was able to report much of McClellan's army's strength and position to Gen. Lee. McClellan was aware of Jackson's arrival and presence at Ashland Station, but did nothing to reinforce Porter's vulnerable corps north of the river.

Lee's plan called for Jackson to begin the attack on Porter's north flank early on June 26. Maj. Gen. A.P. Hill's Light Division was to advance from Meadow Bridge when he heard Jackson's guns, clear the Union pickets from Mechanicsville, and then move to Beaver Dam Creek. The divisions of Maj. Gens. D.H. Hill and James Longstreet were to pass through Mechanicsville, D.H. Hill to support Jackson and Longstreet to support A.P. Hill. Lee expected Jackson's flanking movement to force Porter to abandon his line behind the creek, and so A. P. Hill and Longstreet would not have to attack Union entrenchments. South of the Chickahominy, Magruder and Huger were to demonstrate, deceiving the four Union corps on their front.

Battle
Lee's intricate plan went awry immediately. Jackson's men, fatigued from their recent campaign and lengthy march, ran at least four hours behind schedule. By 3 p.m., A.P. Hill grew impatient and began his attack without orders: a frontal assault with 11,000 men. Brig. Gen. George A. McCall's Union division was forced back. Porter reinforced McCall with the brigades of Brig. Gens. John H. Martindale and Charles Griffin, and extended and strengthened his right flank. He fell back and concentrated along Beaver Dam Creek and Ellerson's Mill. There, 14,000 well entrenched infantry, supported by 32 guns in six batteries, repulsed repeated Confederate attacks with substantial casualties.

Jackson and his command arrived late in the afternoon. However, unable to find A.P. Hill or D.H. Hill, Jackson did nothing. Although a major battle was raging within earshot, he ordered his troops to bivouac for the evening. A.P. Hill, now with Longstreet and D.H. Hill behind him, continued his attack, despite orders from Lee to hold his ground. His assault was beaten back with more casualties.

Jackson did not attack, but his presence near Porter's flank caused McClellan to order Porter to withdraw after dark behind Boatswain's Swamp, five miles (8 km) to the east. McClellan was concerned that the Confederate buildup on his right flank threatened his supply line, the Richmond and York River Railroad north of the Chickahominy, and he decided to shift his base of supply to the James River. (He also believed that the demonstrations by Huger and Magruder showed that he was seriously outnumbered.) This was a strategic decision of grave import because it meant that, without the railroad to supply his army, he had to abandon his siege of Richmond.

Aftermath
Overall, the battle was a Union tactical victory, in which the Confederates suffered heavy casualties and achieved none of their specific objectives due to the seriously flawed execution of Lee's plan. Instead of over 60,000 men crushing the enemy's flank, only five brigades, about 15,000 men, had seen action. Their losses were 1,484 versus Porter's 361. Lee's staff recalled that he was "deeply, bitterly disappointed" by Jackson's performance, but communication breakdowns, poorly written orders from Lee, and bad judgment by most of Lee's other subordinates were also to blame.

Despite the Union tactical success, however, it was the start of a strategic debacle and the unraveling of the Peninsula Campaign. McClellan began to withdraw his army to the southeast and never regained the initiative. The next day the Seven Days Battles continued as Lee attacked Porter at the Battle of Gaines' Mill.