Defense of Mars

The Battle of Mare Erythraeum was a battle where UNSC Army forces led by Colonel James Ackerson fought the Covenant on Mare Erythraeum on the surface of Mars. It occurred simultaneously with the Covenant's prolonged invasion of Earth. During or after the engagement, Colonel Ackerson was taken prisoner and taken aboard the Triumphant Declaration.

Ackerson's work in this battle helped buy UNSC ground forces on Earth precious time.