Friday, June 3, 1864
Union General Ulysses S. Grant planned to attack the Confederate line at Cold Harbor at 4:30 A.M. on Thursday, June 2 only if General Winfield Hancock's Second Corps arrived in time for an attack. However, the Second Corps, engaged in an exhausting 12-hour night march to Cold Harbor, became lost along the way. They arrived at Cold Harbor after dawn, but were too fatigued to engage in battle. General Grant decided to delay the attack until 5:00 P.M. on Thursday and later delayed the attack again until 4:30 A.M. on Friday. These delays would prove extremely costly for the Union Army, as the postponements allowed Confederate General Robert E. Lee to perfect his entrenchments for the coming assault.
At 4:30 A.M. the alarm was sounded for an attack. Grant lined up five infantry corps for the assault, with the Second Corps in position on the left flank. The Twentieth Massachusetts, in Colonel Henry B. McKeen's First Brigade, was in the second line of battle of General John Gibbon's Second Division. On the right of the Second Corps, from left to right, were General Horatio Wright's Sixth Corps, General William F. "Baldy" Smith's Eighteenth Corps, General Gouverneur K. Warren's Fifth Corps, and General Ambrose Burnside's Ninth Corps. Grant had ordered General Smith's Eighteenth Corps to relocate from the Army of the James for the attack at Cold Harbor.
As the infantry units approached the Confederate lines they encountered the difficult nature of the terrain. As they traversed across ravines, marshes, and swamps to reach the Confederate line their regimental formation began to break apart. As the Union infantry came within range of the Confederate lines they were cut down with blistering rifle fire. The Twentieth Massachusetts now found themselves in the front lines. Colonel Henry B. McKeen, commanding their brigade, was killed while leading the charge. Colonel Frank Haskell of the 36th Wisconsin immediately took charge of McKeen's brigade and was also killed. The men of the Twentieth Massachusetts realized the futility of forward assault and rapidly dug entrenchments fifty yards from the Confederate lines. They would remain in this advanced position for days before retreating.1
1Richard F. Miller, Harvard's Civil War: A History of the Twentieth Massachusetts Volunteer Infantry (Lebanon, New Hampshire: University Press of New England, 2005), 376-81.