Joseph Harper

Fleet Admiral Harper was a high ranking UNSC officer in 2552. During The First Battle of Earth, he was direct command of one of the fleets protecting Earth. He was most likely part of the Orbital Defense Grid over Africa, in charge of protecting the MAC orbital platform clusters in that region, which included Cairo Station. Fleet Admiral Harper was not seen on screen, however he was heard in two separate transmissions regarding the attack on Earth, by the Prophet of Regret's battle group (consisting of 15 Covenant Capital Ships: 13 CCS-class Battle Cruisers and 2 Assault Carriers). Harper's transmissions were as follows:

Fleet Admiral Harper: This is Fleet Admiral Harper, we are engaging the enemy!

Admiral Hood: Negative Admiral. Form a defensive perimeter around the cluster.

It is not known exactly how many ships are under the command of Fleet Admiral Harper; but the readout from Cairo Station stated that his fleet consisted of 8 Cruisers and 67 Frigates, as well as a large number of fighter units, as at one point he ordered his Longswords to blanket the Covenant cruisers and take them out one by one.

Though he has the same rank as admiral Hood, Harper is subordinate to the other Fleet Admiral. This is due to the fact that Hood is in command of all of Earth's defenses, and Harper is likely in charge of only a fleet of ships. This is a common practice in the UNSC, officers with more experience can be in charge of other officers with less experience but with the same or even a higher rank.