[dragoon500ly]

Logistics, the boring stuff....

By 1945, the U.S. had committed 21 infantry divisions and 6 Marine divisions. To give an idea how how much shipping was entailed in moving these 27 divisions around....a infantry division had 14,000 men and 2,000 vehicles, which would require roughly 100,000 tons of shipping space to move.

Shipping requirements could be cut by over 40% if the division's equipment was broken down as much as possible and boxed. This method required a fully equipped port (with piers and cranes) at the other end to get all of the stuff off the ships. This explains the critical importance of Hawaii and Australia/New Zealand to the Pacific War effort.

Amphibious landings required four times as much shipping as the boxed method because the hear had to be stored in the order it would be needed and ready to be operated as soon as it left the ship. This is called combat loading. The preferred method was to ship the units to ports boxed, unload them, acclimate the troops and then reload the ships in the combat loading manner.

The rule of thumb used was that for every soldier, airman or Marine sent overseas, they required 12 tons of shipping each to get them over there with their equipment. Thereafter, they each required 1 ton a month of shipping to maintain them in action.

Explaining this another way; to send an infantry division overseas boxed required six Liberty ships. To move the same division into a combat zone required the use of 20 ships of various sizes. A dozen of these would be assault transports, the rest would be LSTs and other specialized amphibious ships.

The 27 divisions sent into the Pacific also required nearly 2,000,000 support troops (and replacements for losses). This meant that over 20 million tons of shipping was needed to get them there and then as much as 1.5 million tons of shipping each month to keep them supplied. The lack of decent ports in the Pacific meany that many of the ships had to make a 12,000 mile round trip in order to reach the fighting fronts.

Another factor that impacted Allied strategic planning was the various speeds of these ships. Consider this...

The Landing Force could maintain a speed of 12 knots.

The Bombardment Group (the old battleships) could sustain 15 knots.

The Escort Group (the CVEs providind CAS) could sustain 12 knots.

The Support Group (the tankers, cargo and hospital ships) could sustain 12 knots.

The Carrier Task Force (the fast battleships and fleet carriers) could sustain 15-25 knots and maintain 30 knots for extended periods of time.

Now then, making allowances for maneuvering, replenishment etc, the Carrier Task Force could cover between 300-500 miles per day. The Bombardment and Escort Groups might manage 300 miles a day. And the Landing Force and Support Group would be lucky to manage 250-miles a day. In addition, submarines often supported operations such as maintaining a scouting screen and picking up downed fliers, they could cover between 200-250 miles a day.

So the admirals commanding had to juggle their various task groups. While the slower groups could basically maintain straight-line steady courses, teh Carrier Task Force often found it self making hugh circles around the ocean, moving back and forth in irregular patterns, in order to provide cover for the slower ships. And in order to confuse the enemy while this dance was ongoing, the Carrier Task Force would often make air strikes on anything within range.