On this date 150 years ago, the first of the Seven Days Battles, the Battle of Mechanicsville/Beaver Dam Creek was fought in the late afternoon and evening. 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.