Cold Harbor Summary: The Battle of Cold Harbor occurred May 31–June 12, 1864, just outside of the Confederate capitol of Richmond, Virginia, during the American Civil War. Cold Harbor was the final battle of Lieutenant General Ulysses S. Grant’s Overland Campaign, which began in early May 1864 with the Battle of the Wilderness. The main part of the Battle of Cold Harbor was a frontal assault on Confederate lines that ended in nearly 7,000 Union casualties after less than an hour—by some accounts most were lost in as little as 10 minutes. It was one of the most brutal confrontations of the war.