Joseph Harper

Fleet Admiral Harper is in direct command of one of the fleets protecting Earth. He is most likely part of the Orbital Defense Grid over Africa, in charge of MAC Platform Cairo. Fleet Admiral Harper is not seen on screen, however is heard in two separate transmissions regarding the attack on Earth, by the Prophet of Regret's battle group (consisting of 15 Covenant Capital Ships: 12 Cruiser Class ships, 1 Supercruiser and 2 Assault Carriers). Harper's transmissions are as follows:

Cortana: Slipspace rupture, directly off our battle cluster.

Admiral Hood: Show me.

Cortana: Fifteen Covenant Capital Ships holding just outside the kill-zone.

In a separate transmission Harper can be heard announcing the following:

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; however he seems to have several Halcyon Class Cruisers, dozens of Frigates, and (apparently) Marathon Class Cruisers under his command, as well as a large number of fighter units, as at one point he orders his men to blanket the Covenant cruisers and take them out one by one.

It is often misunderstood why Fleet Admiral Harper is subordinate to Admiral Hood. Lord Hood, as one of the surviving members of the UNSC High Command, is therefore Harper's superior and commands all of Earth's defensive forces. However, Hood's job appears to be more administrative, whereas Harper has a greater degree of control over the forces he commands. It should also be noted that Fleet Admiral Harper's fleet falls under the Orbital Defense Grid of Earth. Although he is the flagship for his fleet his orders come from either FLEET-COM planet-side or from a MAC station in charge of defense in a given grid, namely the Cairo.