From a report on “The Status of North America”
. . . the decisive incident in the conduct of the war appears to have been the Battle of Cold Harbor. The Federal commanding general had heretofore been successful, albeit at a high cost in manpower. On the morning of June 3, General Grant rode forward to observe the assault of the Federal armies against the Confederate forces of General Lee.
Military operations of such complexity are extremely confusing in such weather as prevailed there at the time. Grant was shot during the beginning of the attack, and was removed from the field almost immediately. In his absence, General Meade, the commander of the Army of the Potomac, which made up almost all the Federal forces engaged, ordered continued attacks, which orders were not carried out by his subordinates.
General Grant’s death that evening meant little to the conduct of the battle. General Meade continued ordering assaults during the next day, which were not carried out by his subordinates. Frustrated by this insubordination, he turned over command to General Warren and proceeded to Washington, where he immediately filed courtmartial charges against Generals Hancock, Wright, and Smith, the three corps commanders in question.
General Warren declined to accept the permanent command, and while the army festered behind its fortifications, the scene of action shifted to Washington, where the generals laid charges against each other, or intrigued for command. General Burnside, the principal commander who had obeyed orders, lobbied for command, but his similar failure when in army command two years previously had made him unacceptable. The other army commander in the area, General Butler, also put forward his name, but he was even more unacceptable.
The position of General-in-Chief was to remain vacant for several more months. General Meade, the victor of Gettysburg, was the most suitable choice from the standard of military ability, but his rancor towards his subordinates made him increasingly unacceptable.
The board of inquiry formed by the Committee on the Conduct of the War to investigate the demise of General Grant could produce no answer. It was suspected, but never proven, that he perished from a shot fired by a Federal soldier who feared being sent forward to his death.
The incursion of the Confederate troops under their General Early, which reached the outer defenses of Washington, caused a panic in the Federal government. Unable to force a conclusion in Virginia, President Lincoln finally was left with no alternative but to order the Army of the Potomac to withdraw to the South Anna River in order to spare troops for the defense of Washington and an invasion of the Shenandoah Valley in reprisal.
This latter was put under the command of General Sheridan. It was reported that General Sheridan was being considered for the position of General-in-Chief, which was why his conduct in the subsequent campaign was tentative and slow. With the immobility of the Army of the Potomac leaving him in some relative safety, General Lee was able to reinforce the Army of the Valley, and stalemate also occurred there.