Interservice rivalry existed in Tokyo, to be sure, but on the fighting front both services cooperated fully, as was evident in Malaya, where General Tomoyuki Yamashita and Admiral Jisaburo Ozawa displayed perfect teamwork. In the Guadalcanal operations, also, the Japanese Army and Navy cooperated.SOURCE: The End of the Imperial Japanese Navy, by Masanori Ito, trans. by Andrew Y. Kuroda and Roger Pineau (Jove Books, 1984), pp. 88-92
The Americans at the front, however, did not yield to each other. One conspicuous example of this occurred when an emergency policy conference was held on 4 September 1942 at Noumea to discuss the Japanese counteroffensive, which was endangering the American forward lines. Present at the conference were Admiral Nimitz, CINCPAC; General Arnold, Air Force Chief of Staff; Admiral Ghormley, Commander in Chief, South Pacific; General Sutherland, Chief of Staff, Far Eastern Army; and General Turner, Commandant of Marine Corps. General MacArthur refused to come to the meeting. When Admiral Nimitz asked General MacArthur for 10,000 soldiers as reinforcements, MacArthur turned down the request, saying that he could not divert a single man from the New Guinea operations—even though he then had 55,000 men under his command. When MacArthur in turn asked Admiral Nimitz for a fleet with two carriers, one Marine division, and a squadron of large bombers for his northward operations, Nimitz refused and explained that operations at Guadalcanal would not permit such a diversion of his forces.
When the situation at Guadalcanal became critical for the United States, President Roosevelt finally took direct measures to dissolve the interservice rivalry. On 24 October 1942 he sent an emergency order, as Commander in Chief of the Armed Forces, directing the immediate reinforcement of Guadalcanal....
Turning to Japan, we see a different kind of rivalry. The battle of the Solomons was fought mainly by the Naval Air Force. Plane losses ran to the staggering total of 7,000. The nation's capacity for plane production should have been mobilized to replenish these losses. The Army, however, insisted on one half of all aircraft production for its own use. Since the Army Air Force had sustained no losses in the Solomons, it should have relinquished its quota to the Navy, but it did not. Two decades earlier, when the Navy under Admiral Tomosaburo Kato was feverishly trying to build its 8-8 Fleet, the Minister of War, General Giichi Tanaka, offered to divert part of his appropriations to assist the Navy's expansion. Such understanding and cooperation, however, could not be expected from the Army leadership of General Tojo. The Navy's antipathy toward Tojo was extreme, and men in the Navy Ministry were correspondingly disturbed by their weak leadership in Admiral Shigetaro Shimada. In the United States, harmony prevailed at the highest level of command, while discord erupted between field commanders. In Japan, on the other hand, there was harmony among field commanders of both various services, but disunity and friction at General Headquarters.
Meanwhile, the scheduled offensives were launched by Admiral Nimitz in the Gilberts and the Marshalls, and by General MacArthur in New Guinea. Japan had no way of knowing which was the main offensive line. She abandoned the Solomons operations, gave up her outer perimeters, and was forced to withdraw to an inner defensive line along the Marianas and the Philippines. This forced withdrawal left Japan with makeshift lines which were indefensible. If she had been content with these inner defensive lines in the first place, and had devoted her efforts to establishing strong positions along these lines, she would have given a much better account of herself.