The Battle of Cold Harbor, the third and final battle of United States Lieut. Gen. Ulysses S. Grant's 1864 Overland Campaign in central Virginia during the American Civil War, today lives in infamy as one of history's most lopsided battles. Grant, the losing general, described it as the "one attack I always regretted ordering."

The battle began on May 31, 1864, when Union cavalry under Maj. Gen. Phillip H. Sheridan occupied the crucial crossroads of Old Cold Harbor, 10 miles (16 km) from the Confederate capital of Richmond. By outflanking Lee's army three separate times, including twice after battles that were actually Confederate tactical victories, they stood at the gates of Richmond. Grant hoped that one more attack might finally break the outnumbered Army of Northern Virginia commanded by Gen. Robert E. Lee.

Over the next two days, the armies of Lee and Grant, having disengaged from a standoff at the North Anna River 10 miles (16 km) to the north, took up new positions around Cold Harbor. Grant, having received heavy reinforcement, brought 105,000 men (the bulk of the Army of the Potomac) onto the field. Lee had also managed to replace many of his 20,000 casualties to that point in the campaign, and his army numbered 59,000. But the disparity in numbers was no longer what it had been—Grant's reinforcements were often raw recruits and heavy artillery troops (pulled from the defenses of Washington, D.C.) unfamiliar with infantry tactics, while most of Lee's had been veterans moved from inactive fronts, and they were strongly entrenched in fortifications.

Grant, unaware of the strength of the Confederate earthworks that confronted his army, directed George G. Meade to mount an assault. Meade and his corps commanders failed to conduct any meaningful reconnaissance of the enemy position. Many of the soldiers were apprehensive about this assault and there are anecdotes that some pinned notes inside their uniforms, meant to identify their bodies after their presumed deaths.

On the morning of June 3, Meade's assault on the Confederate right flank was conducted by three corps, totaling 31,000 men: the II Corps (Winfield S. Hancock), VI Corps (Horatio G. Wright), and XVIII Corps (William F. "Baldy" Smith, part of Benjamin Butler's then-separate Army of the James). The defenders, consisting mostly of men from the Confederate First and Third Corps, who fought from behind earthworks, slaughtered them as soon as they moved forward. One Confederate soldier was quoted after the battle as saying it was "simply murder". The Confederate musket and artillery fire along the XVIII Corps front was so severe that its men were actually pinned to the ground for protection, unable even to retire to their own lines. Union forces lost 4,500 men in about 90 minutes; Grant called off the attacks at midday after visiting his corps commanders, while Meade bragged to his wife the next day that he was in command for the assault.

The next day, Grant launched no more attacks on the Confederate defenses. He later said that he regretted for the rest of his life the decision to send in his men. The two opposing armies faced each other for nine days of low intensity trench warfare. Grant was criticized in the Northern press for refusing to negotiate an immediate temporary truce with Lee for the purpose of gathering bodies and treating the wounded between the lines. On June 12, the Army of the Potomac finally disengaged to march southeast to cross the James River and attack Petersburg, a crucial rail junction south of Richmond.

The Battle of Cold Harbor was the final victory won by Lee's army (part of his forces won the Battle of the Crater the following month, during the Siege of Petersburg, but this did not represent a general engagement between the armies), and its most decisive in terms of casualties. The Union army, in bravely attempting the futile assault, lost 13,000 men over twelve days. The battle brought the toll in Union casualties since the beginning of May to a total of more than 52,000 as compared to 33,000 for Lee.

The battle was fought over the same ground as the Battle of Gaines' Mill during the Seven Days Campaign of 1862. In fact, some accounts refer to the 1862 battle as the First Battle of Cold Harbor, and the 1864 battle as the Second Battle of Cold Harbor. Soldiers were disturbed to discover skeletal remains from the first battle as they entrenched. Despite the name, Cold Harbor was not a port city. It was named for a hotel located in the area which provided shelter (harbor), but not hot meals.

The battle caused a rise in anti-war sentiment in the Northern States. Grant became known as the "fumbling butcher" for his poor decisions. It also lowered the morale of his remaining troops. But the campaign had served Grant's purpose—as foolish as his attack on Cold Harbor was, Lee was trapped. He beat Grant to Petersburg, barely, but spent the remainder of the war (save its final week) defending Richmond behind a fortified trench line: see Siege of Petersburg. The end of the Confederacy was just a matter of time.