'Ko' was a Japanese offensive in central China, launched as the first of the three components of the 'Ichi' strategic offensive, whose other components were the two parts of 'To' (iv) fought farther to south (17 April/June 1945).

The operation was planned in Peking and Nanking by General Yasuji Okamura’s China Expeditionary Army with the object of eliminating the Chinese salient to the north of the Yangtse river, and thereby clearing the strategically vital rail line linking Chengchow and Hankow. The shoulders of this salient were at Tungkwan in the north and near Laohokow in the south, and its apex jutted into the Japanese-held portion of China as far east as Kaifeng in the sector held by Lieutenant General Takari Takamori’s 12^th Army and Lieutenant General Senichi Kushibuchi’s 34^th Army of General Naosaburo Okabe’s 6^th Area Army.

This Chinese salient was an important Japanese target for the three reasons that it contained a valuable rice harvest, sheltered the two major bases of Major General Claire L. Chennault’s US 14^th AAF at Ankang and Laohokow, and included the strategic rail nexus of Chenghsien. The rice harvest was important to the Japanese as it would bolster their capabilities while reducing those of the Chinese from whom it could hopefully be captured immediately after the harvest, the reduction of the air bases would lessen the threat to significant Japanese targets in China and Manchukuo (the Japanese puppet state in Manchuria), and the capture of Chenghsien would allow a useful reduction in Japanese local force strengths by allowing greater strategic mobility and speed as lines radiated from this key city to Peking in the north, to Tungkwan and Sian in the west, to Hankow, Wuchang, Changsha and Canton in the south, and to Suchow and Haichow in the east.

Otherwise known as the Battle of Central Henan, 'Ko' was the first part of 'Ichi', and involved substantial Japanese forces under the local command of Lieutenant General Eitaro Uchiyama’s 15^th Area Army against a smaller Chinese strength under the local command of Lieutenant General Tang En-po, the deputy commander of General Chiang Ting-wen’s 1^st War Area, for the defence of the strategic position of Luoyang.

In 'Ko' the Japanese committed some 390,000 men of Lieutenant General Yuichiro Nagano’s 37^th Division of Lieutenant General Teiichi Yoshimoto’s 1^st Army and Lieutenant General Jinkuro Ochiai’s 27^th Division, Lieutenant General Takeo Fujioka’s 62^nd Division, Lieutenant General Yoshitaro Hayashi’s 110^th Division, Lieutenant General Hideo Yamaji’s 3^rd Armoured Division, the 7^th Independent Mixed Brigade, the 9^th Independent Mixed Brigade and the 4^th Cavalry Brigade of the 12^th Army as well as some 230 aircraft of the 5^th Air Army.

The Chinese-held area threatened by 'Ko' was the responsibility of Chiang’s 1^st War Area, though Tang, Chiang’s deputy, exercised operational command of most of the Chinese ground forces involved in 'Ko', which totalled about 100,000 men 1.

'Ko' began on 17 April as an advance across the Huang river into Henan with the object of clearing the railway between Chengchow and Hankow. The attacking force was spearheaded by three infantry divisions and the 3^rd Armoured Division of Uchiyama’s 12^th Army, and was supported by several independent mixed brigades. The Japanese spearheads crossed the Huang river around Zhengzhou late in April and defeated the Chinese forces near Xuchang, then wheeled to the west to besiege Luoyang, which was defended by three Chinese divisions. The 3^rd Armoured Division began to attack Luoyang on May 13 and took it on May 25, and the railway had been secured by June. The 30 Chinese defending divisions enjoyed no support from the people of Henan, who were embittered by continuing taxation during a period of famine, and were allegedly alienated still further from the nationalist cause by communist collaborators.

Thus 'Ko' was more than an adjunct to 'Ichi', having decidedly important strategic ramifications of its own, and great efforts were made by the Japanese to secure success. The operation came as a complete surprise to the Chinese, who were forced back throughout the salient, especially in the south where the air base of Laohokow fell, much to the chagrin of Chennault. However, the Chinese had started to check the Japanese thrust by a time in the middle of June 1945 as a result of the rejuvenating efforts of Lieutenant General Albert C. Wedemeyer, who had succeeded Lieutenant General Joseph W. Stilwell as chief-of-staff to Generalissimo Chiang Kai-shek during the earlier stages of 'Ichi' and was also exercising operational command of the Chinese forces in the field.

At about this time Okamura decided that the offensive warranted no further expenditure of Japanese effort and resources, for the rice harvest had been captured, Chenghsien taken, and one of the two US air bases in the area seized. Moreover, the threat along the Siberian/Manchukuoan border was looking increasingly dangerous as Soviet troops were moved into the theatre at the time of terminal hostilities in Europe, so Okamura decided to use the strategic mobility provided by possession of Chenghsien to reduce his forces in China to bolster those in Manchukuo.