The fourth phase of U.S. Grant’s overland campaign against Robert E. Lee. Grant had spent all of May attempting to get past Lee’s right flank, suffering and inflicting heavy casualties on the way (Battles of the Wilderness, Spotsylvania and North Anna River). However, by Cold Harbor, both armies had been reinforced back up to their original sizes (although on both sides some of these reinforcements came from other armies). For many in the north, Grant was failing just as badly as his predecessors, and at much higher cost.
In reality, Lee’s army was being badly mauled. He was losing experienced officers at a dreadful rate. The pool of potential reinforcements was being to run dry. After the Battle of the Wilderness his army rarely took the initiative, instead tending to wait in its defences for Union attacks. This tended to cancel out Lee’s own great abilities, removing the chance for him to influence a battle with a flash of inspired strategy. Each apparent Union ‘failure’ was driving Lee back towards Richmond and a potential siege. Grant’s simple refusal to be beaten now began to pose a potentially mortal threat to Lee’s army.
Grant’s army had also suffered during May. Combat had been so intense and so constant that men began to develop shell shock, more familiar from the Western Front. Just as Lee’s army was beginning to lose its ability to attack, Grant’s was beginning to slow down. This was to cost it dearly at Cold Harbor (and again soon after at Petersburg).
This was not immediately apparent. On 31 May Sheridan’s cavalry managed to force a Confederate force out of Old Cold Harbor. The next day he was able to hold on until the first infantry units began to arrive to reinforce him. Grant now ordered his army to concentrate at Cold Harbor, with the hope of launching an attack on 2 June. He was to be disappointed in this. Partly due to exhaustion and partly due to confusion on the roads, the Union army was not in place in time for an attack on 2 June.
3 June saw one of only two attacks that Grant admitted to regretting ordering (the other was the second assault on Vicksburg). By 3 June, Lee’s men had had time to fortify their seven mile long line using all the experience gained over the last month. Despite an almost 2-1 advantage in numbers (although not in the actual attack itself), Grant’s men had no chance of success unless their enemy was utterly demoralised. The attack went forward early in the morning of 3 June. In one hour of fighting the Union army suffered 7,000 casualties. Confederate losses were at most 1,500. Although the two armies stayed in the trenches around Cold Harbor for some days after 3 June, the failed assault effectively ended the battle.
With it ended the overland campaign against Richmond. There was very little potential left for flanking manoeuvres in the vicinity of Richmond, and the swamps around the Chickahominy were just as big a barrier as they had been two years earlier. However, one of the many ways in which Grant differed from McClellan was that he was not easily discouraged. Once it was clear that he would not achieve his aims outside Richmond, he began to look for another target. He soon found that target. In mid-June, Grant’s men crossed the James River, shifting the focus of their attack from Richmond to Petersburg.