The first battle (June 27, 1862), sometimes called the Battle of Gaines's Mill, was part of the Seven Days' Battles (June 25–July 1), which ended the Peninsular Campaign (April 4–July 1), the large-scale Union effort to take Richmond. After fighting at Mechanicsville and Beaver Dam Creek, General George B. McClellan (McClellan, George B) ordered Union troops to high ground between Gaines's Mill and Cold Harbor. When Confederate General Robert E. Lee (Lee, Robert E.) attacked on June 27, the Union troops were driven back in disorder and withdrew to the south side of the Chickahominy River.

The second Battle of Cold Harbor (June 3–12, 1864) is considered one of the worst tactical defeats suffered by the North in the Civil War, though its subsequent effect was negligible. Following the Battle of Spotsylvania Court House (May 8–19), Union General Ulysses S. Grant (Grant, Ulysses S.) advanced southward toward Richmond in a series of flanking movements. Confederate troops under Lee at Cold Harbor entrenched themselves in defensive positions behind earthworks. From these, Union assaults were repulsed with heavy losses. Because of Grant's vast numbers (more than 100,000 men), his losses of about 7,000 (compared with fewer than 1,500 for Lee) did not deter him from continuing to Petersburg (Petersburg Campaign) later that month in his drive toward Richmond.