The US Navy does not have the numbers - capability and capacity - it used to have at its zenith in the late cold war. There has not been a dedicated replenishment (AOE/AOR) ship assigned to CSGs for the last 15-20 years. The ARGs never had one. The model was upended when the the AORs and most AOEs were decommissioned. The T-AOs and T-AKEs were not a one for one replacement in capability/capacity.

Typically underway replenishment is accomplished by theater assets called delivery ships that that sail out from the designated logheads to provide support. The tyranny of distance from the logheads is a key factor. The threat and vulnerability of the replenishment ships, sea lines of communications (SLOCs) and logheads is also a factor.

That drives where ships can replenish, when, and how often. Some ships maybe operating in a high enough threat area that they need to be rotated off station to replenish - another numbers game. Having been on the staff managing the escort of reflagged tankers in the Persian Gulf in the late 1980's I saw it first hand. We had a station in a high threat area which we referred to as "Ethiopia Station" because we could not risk a replenishment ship to resupply them. Ships on that station suffered acute shortages.

Also, when considering the issue, we must think globally. To support the logheads is a network of ships and aircraft to shuttle cargo into theater from as far away as the US. Mail is another related challenge. This theater is just the current salient example. It is small compared to the challenges in the Western Pacific.

As Gen Omar Bradley said: "Amateurs study tactics; professionals study logistics."