Differences in World War II allied strategies for Europe and the Pacific: In the Pacific, because of the long distance from allied bases to Japanese targets, and because of the ocean separating different Japanese targets, it took about three times as many ships to move and support a given number of allied troops as it took to move and support the same number of troops in the European theatre where great Britain was just a few tens of miles from Europe.  So plans between the two theatres had to differ in the number of ships committed.

Also, in Europe, Russia was fighting the Germans and appeared to be getting whipped.  The loss of Russia as an ally against Germany would have meant the loss of many soldiers to fight Germany and the capture of many war resources for Germany to use against Britain and USA.  Thus USA and Britain agreed to fight Germany first, then turn on Japan.  Actually USA ended up fighting both Germany and Japan at the same time, but USA gave more to its fight against Germany until Germany was defeated, then gave all to fighting Japan.  So, plans for Europe and Pacific had to differ as to which got the most war resources first.

The United States Navy and Marine Corps would take the brunt of the action in the Pacific theatre of World War II, compared with the mostly land war that would be fought in Europe. Prior to the D-Day Invasion, the Allied forces had already been awaiting action in England, just a few short miles from the Normandy beaches. In the Pacific, troops would have to land in piecemeal fashion, especially when they had to attack the heavily defended islands such as Iwo Jima and Guadalcanal. The Marines played a major part in the land battles, while the Navy took on a much larger responsibility than in the European theatre. 

The most important thing here is that planning for fighting in Europe was relatively simple.  Not that it was easy or anything, but it was easier than planning for the Pacific.

the major reason for this was the distances involved.  Once you get all the materials to England, all you have to do is to get them over to the continent, which is very close.  On the continent, all the fighting is going to occur in a very small space, relatively speaking.

Out in the Pacific, there were huge spaces of ocean separating the US from the places the battles would happen.  And there were large distances separating one battle site from another.  This made planning quite difficult.