Battle of Cleveland
From Halopedia, the Halo wiki
The Battle of Cleveland was an engagement between the UNSC Defense Force and the Covenant Military that took place in Cleveland, Ohio on Earth. [1] The purpose of the raid was the retrieval of the Key of Osanalan, a Forerunner artifact revealed by Colonel James Ackerson during his interrogation. It was a necessary component for the firing sequence of the Halo array to properly initiate it.
It is a smaller battle during the Second Battle of Earth.