The U.S. counteroffensive across the Pacific was driven by three major factors: geography, resources and personalities. The simultaneous drives began with limited operations designed to secure the approaches and security of Australia, America’s prime Pacific ally; then diverged as America’s capabilities and resources increased and reconnected again in the final phases of the war as the U.S. prepared for an invasion of the Japanese islands.
Personalities were the early driving factor in how command was allocated in the Pacific Theater and how the war would be fought on a strategic level. After being driven from the Philippines, General Douglas MacArthur was sent to Australia to organize the first American troops in theater and prepare to defend the continent. Even though naval power would be the major weapon in the drive through the central and northern Pacific to an eventual invasion of Japan, MacArthur was not about to report to Adm. Chester Nimitz, so a convoluted command structure was set up to accommodate all the big egos in the Pacific. Although this command structure worked fairly well, and the U.S. was able to provide enough manpower and material to support two simultaneous drives, the command and ego issues would remain throughout the war; coming to a head in early 1944 when the major commanders discussed whether to invade the Philippines or Formosa. [FTCD, 422-423, 427]
Each offensive had its own unique features, mainly driven by geography and available resources. The Southwest Pacific campaign led by MacArthur was primarily an army operation, since Army divisions were available in mid-1942 and airfields were always available for land-based air power to support his drive. The Central Pacific Campaign was more of a joint operation, combining naval forces led by carrier-based airpower, land-based bombers and Army infantry and Marine divisions to conduct amphibious landings on heavily defended island chains. In the initial counteroffensives through the Solomon Islands and up New Guinea to keep lines of communication open to Australia, both drives depended upon land-based air power to support what were primarily infantry battles to capture and hold airfields or areas to build airfields. Both drives also depended upon amphibious operations to bypass heavy Japanese defenses and land troops around hostile geography. Once the Navy made good on their heavy losses from the Solomons campaign, the Navy-Marine Corps teams honed this to a fine art, utilizing “island hopping” to cutoff strong Japanese positions such as Rabul and Truk and establish fleet anchorages and air bases to keep the offensive moving. After 1943 as the operations diverged and the Navy began moving more into the Central Pacific to attack the Marshalls and Marianas, the Navy was actually able to supplant the need for land-based bombers with sufficient carrier air power to both support land operations and be able to defend against the remnants of the Japanese Navy. MacArthur continued to rely almost exclusively upon his Fifth Air Force to provide air support during his drive up New Guinea, and utilized his small naval force mainly to outflank Japanese positions along the coast. [FTCD 427, 441-443, 452-454]
Although the two advances were initially motivated as much by military politics as reasoned strategy, they ended up complimenting each other by keeping the Japanese off balance and under constant offensive pressure. A single thrust may have allowed the Japanese to concentrate their more limited resources and make offensive progress more difficult. This can be seen in the Leyte landings of October 1944, the reuniting of MacArthur’s and Nimitz’s forces where Halsey’s 3rd Fleet provided naval and air support to MacArthur’s 6th Army landings. The Japanese were able to concentrate their entire remaining naval power, numerous kamikazes and their massive army in the Philippines to provide their best opportunity to stop or severely delay America’s offensive drive. Only the incredible sacrifices of the escort carrier groups and the loss of nerve by the Japanese Admiral Kurita during the Battle of Leyte Gulf saved the U.S. from an embarrassing defeat on the scale of the Battle of Savo Island and the potential loss of the beachhead at Leyte. [FTCD 460-466]
Overall the strategy pursued by the U.S. worked well, and our industrial might was able to support what seemed like redundant operations in the Pacific Theater. By advancing on two axes, the Japanese were cutoff from the resources of Indonesia and Southeast Asia by MacArthur’s drive while losing most of their naval forces fighting off Nimitz’s naval thrust across the Central Pacific. A single thrust advance would probably not have been as successful and would likely have delayed serious offensive action since the U.S. was not able to build up a sizeable fleet from the naval losses around the Solomons until mid-1943. Having a single commander in chief with the same authority Eisenhower had in Europe may have made coordination easier, but the scale of the fighting in the Pacific, combined with the competing agendas of the Army, Navy and eventually Army Air Forces when the 20th Air Force and their B-29s arrived in the Marianas made this impossible.
If the U.S. had continued with an eventual invasion of Japan, watching how the command structure unfolded would have been very interesting.
Footnotes from For the Common Defense by Allan R.Millett and Peter Maslowski.