The US and her allies did not have enough men and material to cover the entire ocean. A successful invasion entailed coordinating ground, sea and air forces from all of the united nations across the vast expanse of the Pacific. Planning an invasion took more time than executing it. Several invasions could be planned in the time it took to execute one. Experience gained by the allies in clawing their way up New Guinea showed that combat ships were too valuable to leave idle during the planning phase. They also had no extra room to provide for all the extra personnel from the various forces needed to organize the invasion forces.

Enter a new class of ship, the Auxiliary General Communications ship. The name, like the appearance, was deceptive. It was designed to look like a supply ship. The crews were told to not reveal the nature of the mission. Even today, there is not a lot of information available on the AGC fleet. It was lightly armed so as to not attract attention, but they held the brains behind the amphibious assault groups.

The details of an invasion would be planned by the assault commanders on each of the Pacific AGCs according to strategic directions. The invasion date would be decided on and forces would converge from across the Pacific on the target site on the date planned. The amphibious planning groups were never large but the forces they could muster were. This enabled the fighting groups, which were resupplied while at sea, to always be free to fight.

A fighting force would finish a landing one day, be assigned a new task force name and be steaming off to the next fight under a different admiral the next. The following table, which shows united nations landings in the Phillipines in the last year of the war shows just how mobile and effective the Phib groups became in clearing out the Japanese.

US ships spent very little time in port compared to the British and Japanese in large part because the AGC command brought planning down to the grass root level. It also enabled the united nations forces to deploy overwhelming air, sea and land forces at each invasion they undertook. This could not have been done if each 'Phib' group had its own army, its own navy and its own air force.