I'm going to focus on the criticism of Japanese tactics in the defense of Okinawa, as well as a general overview of the doctrine of the Imperial Japanese Army (IJA) and the general strategy of Japan in World War II for context.

To start with, I've talked about the IJA's doctrine here. To summarise, the IJA's doctrine was built around overcoming the undeniable economic reality that Imperial Japan lacked the ability to compete with its likely rivals (from the Army's perspective the Soviet Union) on a material basis. As such, the IJA sought to overcome this material inferiority with spiritual superiority. The enemy may have more and better weaponry and equipment, but the Japanese soldier would have a greater will to fight and would thus be willing to sacrifice more in order to achieve victory. To that end, IJA tactics were all about offensive action, to rely upon the greater fighting spirit of the Japanese soldier to quickly achieve victory, before the drain of attritional warfare could come to bear.

The overall Japanese strategy in the Pacific War had remained the same, though it had changed somewhat in execution. Japanese leadership had always known that they had no ability to compel the U.S. to surrender. The thought of Japanese soldiers landing in San Francisco, let alone advancing into the United States was laughable. Instead, the Japanese plan was to make the costs of war with Japan too high for the United States to pay, and that the U.S. would come to a negotiated settlement favorable to Japan. Originally, the Imperial Japanese Navy (IJN) had hoped to accomplish this via a decisive battle with the U.S. Navy. However, the campaigns of 1942--in particular the defeat at Midway and the extended Solomon Islands campaign--had weakened the IJN, while the superior economic output of the U.S. had come to bear. Thus, when the Japanese had tried to stage the decisive battle in defense of Saipan, the resulting Battle of the Philippine Sea had been a disaster for Japan, permanently crippling the IJN. However, despite this, the hope of making the cost of war too high for the U.S. to bear had remained the main goal of the Japanese military, in the hopes of bringing the U.S. to a negotiated settlement.

With that in mind, it's worth noting that the Japanese goal in defending islands like Okinawa and Iwo Jima was no longer "keep the U.S. off the island" or "keep the islands airfield in operation" it was "hold out as long as possible to buy more time for the preparation of defenses on the Home Islands and inflict as many casualties on the U.S. as possible to underline Japanese." The hope was that by bleeding the U.S., the Americans would opt for a negotiated settlement, rather than insisting on unconditional surrender and risking an invasion of the Japanese Home Islands. To that end, let's examine how Japanese island defense doctrine had evolved over the course of the Pacific War. In the beginning of the war, the IJA hadn't really had a special doctrine for the defense of islands. Rather, the IJA had simply adapted its guidelines on defending rivers to the defense of islands. This called for forward defenses on the waterline, with strong counterattacks intended to drive the enemy back into the sea. While this had indeed caused heavy casualties for U.S. forces landing on islands like Tarawa, it also meant that the battles for these islands were relatively short. The sheer amount of firepower that the U.S. could bring to bear, and their flexibility in being the attacker meant that--while the U.S. might suffer losses--they would almost certainly be able to force a landing somewhere on the island. Furthermore, Japanese forward defenses and counterattacking were more exposed to fire support from aircraft and ships, which helped blunt these attacks. This meant that once the Americans were ashore, they could relatively easily roll up Japanese defense now trapped in forward fighting positions or defeat Japanese counterattacks, quickly--if bloodily--securing the islands. However, Japanese doctrine was evolving, as shown by examples such as the extended defense of Peleliu. In October 1944, the IJA published an updated manual on counter-amphibious attack, which called for avoiding a defense of the waterline, and instead opting for a mobile defense of well fortified interior positions. Remaining on the defensive would avoid exposing Japanese forces to American firepower, and instead force the Americans to attack into well prepared defensive fortifications in depth. Indeed, the new doctrine seemed quite successful at Iwo Jima, for the first time in the island hopping campaign, the Americans suffered more casualties than the Japanese.

I've only talked about here how Japanese tactics for island defense evolved over the course of the war, and the guiding principle behind those changes in tactics. Suffice it to say, Japanese tactics were heavily constrained by the situation they found themselves in, as Japan had always had issues in equipping its forces, due to its limited industrial base. However, Japanese tactics overall can be pointed back to the guiding principles of the IJA, which had always emphasised superior fighting spirit, manifested in aggressive offensive action to bring about quick victories. This is not to even touch on the IJN, which arguably had the world's most effective carrier doctrine in 1941 or general Japanese air doctrine. It's always worth noting that American observers often mischaracterised Japanese actions, both due to racist stereotypes of the Japanese, and their own lack of knowledge as to the factors the Japanese were trying to overcome. A classic example of this comes from the air war, where Allied observers would routinely characterises Japanese aircraft as attacking in uncoordinated "swarms". However, from the Japanese perspective, they were flying in well ordered formations, but the lack of effective radio meant that aircraft were constantly maneuvering in order to maintain situational awareness and ensure pilots were watching all approaches. To the Allied point of view, this maneuvering seemed as though the Japanese were flying without formation at all. I would not be overly reliant on first hand American accounts of Japanese tactics to criticise those tactics.