The Japanese High Command realized that the loss of Okinawa would give the Americans a base for the invasion of Japan. Its desperate response to the invasion of Okinawa was to unleash the full force of the Special Attack Units, known in the west as the Kamikaze ('Divine Wind'), in the hope of inflicting punishing casualties on the US Pacific fleet that in turn disrupted the invasion. In a series of mass attacks in between April and June 1945, more than 900 Kamikaze aeroplanes were shot down. Conventional fighters and bombers accompanied the Special Attack Units as escorts, and to add their own weight to the attacks on the US fleet. In the air battles leading up to the invasion of Okinawa, as well as those that raged over the island in the three months, that followed, and in strikes on Japanese airfields in Kyushu (the base of the Special Attack Units), the Japanese lost more than 7000 aircraft both in the air and on the ground. In the course of the fighting, 67 Navy, 21 Marine, and three USAAF pilots became aces, destroying at least five aircraft between March and June 1945. In many ways it was an uneven combat. While many regular Japanese Army and Navy aviators volunteered for the Special Attack Units, a large number of the pilots in the Special Attack Units were inexperienced and only recently out of flying training. They also often flew obsolete aircraft. These less experienced pilots were no match for the Hellcat, Corsair and Thunderbolt pilots who were at the peak of their game. Indeed, many of the latter had been flying fighters for two or more years, and had previous combat experience. On numerous occasions following these uneven contests, American fighter pilots would return from combat having shot down up to six Japanese aeroplanes during a single mission. Indeed, during the campaign 13 Navy, five Marine Corps and two USAAF pilots became 'aces in a day'.