Why was the battle of cold harbor fought?

The Battle of Cold Harbor in early June, 1864 was one battle in the so-called "Overland Campaign". The battle was an attempt by General Grant to dislodge General Lee's troops which were intrenched in defensive positions. Grant ordered his soldiers to attack the Confederates. In about twenty minutes 7,000 Union soldiers fell(killed and wounded). This attack was the only one that Grant later said he regretted ordering.