Hello all! I've been an AH enthusiast for a while, but this is my first post.
OTL, the US divided its resources in the Pacific between two fronts: First, MacArthur's Southwest Pacific Offensive aimed at isolating Rabaul and liberating the Philippines. Second, Nimitz's Central Pacific Offensive aimed at capturing islands close enough to Japan to bomb them into submission and threaten them with invasion. I'm working on a TL in which the US goes with Nimitz's USN/USMC offencive in the Central Pacific, and simply holds the line in the South rather than take the offensive.
If the US went with Nimitz's strategy exclusively, the Marines almost certainly would've taken the lead as in OTL. But would it have been possible for the USMC to take the Gilbert, Marshall, and Marianas Islands, as well as Iwo Jima and Okinawa, with little to no Army help?
As far as I can tell, there were never more than 5 divisions in the Gilbert/Marshall and Marianas Islands Campaigns and Iwo Jima (I'm discounting Peleliu, because that would be unnecessary without MacArthur's offensive). Six divisions fought on Okinawa.
According to Wikipedia, The 1st, 2nd and 3rd Marine divisions were active by new year's 1942. There was also the Paramarine Regiment, the 1st Provisional Marine Brigade, and the Marine Raider Regiment, which constituted enough forces to form a fourth division. In addition, the 4th, 5th and 6th Marine Divisions were formed in August, September and November of 1943, respectively.
This yields the following forces for the Marine Corps:
before August 1943: 4 Divisions
August-September 1943: 5 divisions
September-November 1943: 6 divisions
after November 1943: 7 divisions
So what do you think? Would the US go for an exclusively Marine and Navy offensive in the Central Pacific, with the Army relegated to supporting the Marines and holding the line in the south? How would this affect the rest of WWII? With the shipping used in the Solomons OTL freed up, would this open the door for a 1943 D-Day? Would this speed up or extend the war?