'Ten' was the Japanese plan for the air defence of Okinawa and the Japanese home islands (January/August 1945).
In its initial form, 'Ten' was devised by the Imperial General Headquarters as a means of co-ordinating more closely the air defence assets of the Japanese army and Japanese navy under the former’s 1st Air Army, commanded by Lieutenant General Takeo Yasuda. This formation controlled Lieutenant General Kihachiro Yoshida’s 10th Air Division, Lieutenant General Kumao Kitajima’s 11th Air Division and Major General Yasuyuki Miyoshi’s 12th Air Division (400 fighters and 45 reconnaissance aircraft) allocated respectively to General Keisuke Fujie’s 12th Area Army, General Masamitsu Kawabe’s 15th Area Army and Lieutenant General Isamu Yokoyama’s 16th Area Army. It also supervised various naval fighter units totalling 160 aircraft.
It was appreciated, however, that these forces could hope to deal, at best, only with the US strategic bomber offensive from bases in the Mariana islands group, and that further air assets would have to be deployed for attacks on the fleets of warships, amphibious assault ships and craft, and support vessels which the Allies would deploy for the invasion of Japan which would inevitably come.
By March 1945, therefore, Imperial General Headquarters had developed 'Ten' into an offensive/defensive scheme for air attacks designed to destroy US invasion forces before they could land on Japanese soil. The formations tasked with this responsibility were Vice Admiral Kinpei Teraoka’s 3rd Air Fleet, Vice Admiral Matome Ugaki’s 5th Air Fleet, Vice Admiral Minoru Maeda’s 10th Air Fleet, and Lieutenant General Michio Sugawara’s 6th Air Army in Japan, Vice Admiral Takijiro Onishi’s 1st Air Fleet and Lieutenant General Kenji Yamamoto’s 8th Air Division in Formosa, and units of Lieutenant General Takuma Shomoyama’s 5th Air Army in China.
Naval air units were tasked with attacks on US naval forces, while army air units dealt with the amphibious forces.
The Japanese also appreciated that kamikaze attacks offered them the best chances for success, and all air formations involved in 'Ten' were instructed to inculcate such a spirit among their pilots. In keeping with this tactical decision the 10th Air Fleet was fully equipped with kamikaze aircraft (700 machines by the end of March rising to 2,000 machines by the end of April), and the 6th Air Army included about 350 such aircraft in its total of 700 machines.
It was also decided by Imperial General Headquarters that as the situation in the Southern Region was essentially hopeless, the theatre’s air assets should be returned to Japan for more profitable employment. Thus Imperial General Headquarters ordered Field Marshal Count Hisaichi Terauchi’s Southern Expeditionary Army Group to return six air regiments from Lieutenant General Seiichi Terada’s 2nd Air Division in the Philippine islands group, the 30th Fighter Group from the Philippine islands group, the transport element of the 1st Airborne Group in the Philippine islands group, two air regiments and one heavy bomber squadron from the Lieutenant General Einosuke Sudo’s (from 1 February Lieutenant General Shigeji Hakugin’s) 7th Air Division on Celebes island, and one heavy bomber squadron of Lieutenant General Hidenobu Hashimoto’s 9th Air Division on Sumatra.
The much-reduced 2nd Air Division and 7th Air Division were allocated to Lieutenant General Bin Kinoshita’s 3rd Air Army, and the personnel of Lieutenant General Yoshizo Mikami’s 4th Air Division and 1st Airborne Group were transferred as infantry to General Tomoyuki Yamashita’s 14th Area Army in the Philippine islands group as their original formations were now bereft of aircraft.
By the end of March 1945, therefore, 'Ten' could call on some 2,100 army and 3,100 navy aircraft for the defence of Japan against US attack. What 'Ten' could not provide, however, was adequate fuel for sustained operations or for the continued training of the mass of aircrews required, whose standards can be described only as poor.