'Carbonado' was the US and Chinese revised version of 'Beta' and then 'Rashness', and as such the offensive by Chinese forces to clear the Japanese forces from the region of Canton and Hong Kong and take Fort Bayard, and with then, with these ports available for the maritime sustenance of the Chinese armies, advance to the north-east to take Shanghai (7 June/15 August 1945).
The cover plan for 'Carbonado' was 'Iceman', which detailed a Chinese undertaking to take Hong Kong in the autumn of 1945. Both plans were revealed to the Chinese, at the same time but with no indication which was the real plan, to improve security in case there was a leak of information from the Chinese.
The scene started to be set for the 'Carbonado' concept in the middle of April 1944. At this time the Japanese Imperial General Headquarters was faced with the problem of its response to the latest Allied operations in South-East Asia, South-West Asia and the Pacific. At this time the US forces had completed their 'Detachment' seizure of Iwo Jima and had landed on Okinawa in 'Iceberg', which could provide staging bases for attacks on the Japan home islands themselves, and the weight of bombs falling on the home islands from Boeing B-29 Superfortress heavy bombers operating from the Mariana islands group, take by US forces in 'Forager', was crippling the Japanese war-making industries and shattering Japanese cities and transport.
A short-term consequence was the Japanese implementation 'Ketsu' as reflected by the order of Imperial General Headquarters that General Yoshijiro Umezu’s (from 18 July General Otozo Yamada’s) Kwantung Army in Manchukuo to transfer 33% of its ammunition and some of its best troops to the home islands. Tokyo also issued warning orders to Field Marshal Shunroku Hata’s China Expeditionary Army to ready itself to concentrate this army group’s strength in the Yangtze river valley between Shanghai and Hankow, around the main ports of China (including Canton and Shanghai), and across northern China in collaboration with the remaining formations of the Kwangtung Army. This latter was to be reinforced with newly mobilised formations from the home islands, raining its troop strength by the summer of 1945 to more than 1 million men in the regions to the south of the Great Wall, although the quality was less than before.
The redeployment within China was designed to guard against the likelihood of US amphibious assaults along the coast of mainland China and a Soviet attack from the north. The Japanese leaders thus hoped to deny the Allies the staging areas from which they could attack Japan, and at the same time to protect Chinese mines and factories, which could still supply Japan’s military forces.
Thus, when the Japanese 'Ichi' drive on Chihchiang was blunted and pushed back, reinforcements were not rushed to the area to retrieve the situation, as the local commander demanded. Instead, the Japanese prepared for further withdrawals. In the middle of May, as the Japanese situation on Okinawa continued to deteriorate, Imperial General Headquarters ordered the evacuation of the southern rail line extending to Kweilin and Liuchow, a branch of the main line linking Hankow and Canton. Thus, within a few days of the end of the 'Ichi' campaign, Okamura had begun to move units from south China and redeploy them into northern and central China.
As the Japanese forces began to pull back, Lieutenant General Albert C. Wedemeyer, chief-of-staff to Chiang Kai-shel and commanding the US forces in China, and his China theatre planning staff began to examine how best to exploit the Japanese withdrawal, and decided that a revival of 'Beta', for an advance to the coast to capture the ports of Canton and Hong Kong, offered considerable possibilities. With major US forces now established in the Philippine islands group as a result of the various 'King', 'Mike' and 'Victor' undertakings, the shipment of large tonnages of supplies to China was no problem. Moreover, the clearly imminent Japanese evacuation of the air bases in the area of Kweilin and Liuchow, some 270 miles (435 km) to the west of Canton, would further aid in the solution of any logistical problems that might appear in the execution of the offensive. Supplies then could be flown directly from India or the Philippine islands group into the eastern part of China.
The revised plan, renamed 'Carbonado', called for a rapid overland advance to the coast in August to seize Fort Bayard on the Liuchow peninsula, about 250 miles (40 km) to the south-west of Canton. Once a forward supply base had been established at Fort Bayard, Wedemeyer believed, the main 'Carbonado' offensive could begin on 1 September from the area of Kweilin and Liuchow to allow a final assault on Canton on 1 November.
Additional combat aircraft arrived in China to prepare for and support 'Carbonado'. Major General Howard C. Davidson’s US 10th Army Air Force from India joined Major General Claire L. Chennault’s US 14th AAF on 23 July to form the Army Air Forces, China Theater, under the command of Lieutenant General George E. Stratemeyer. Logistical support was another matter, and proved to just as difficult as ever it had been in the China theatre.
As the Chinese followed the retreating Japanese, it quickly became clear that while air resupply could provide ammunition in the quantities which were needed, it could not feed entire Chinese armies. Parts of the countryside contained no food whatsoever, the Japanese having adopted a 'scorched earth' policy in their retreat, and a ground line of supply had therefore to be crated to move food supplies forward.
The organisation of an effective land-based logistical system for a sustained offensive demanded that preparations had to be made all the way between India and Kunming, and the whole process was further complicated by the fact that operations along the land route through Burma were severely hampered by the rains of the south-west monsoon between April and October.
Despite these problems, the troops of Lieutenant General Daniel I. Sultan, the commander of the India-Burma Theater, provided steadily increasing support for the China effort. With combat operations in Burma drawing drawing toward their end, Sultan’s command became, in effect, the support agency for Wedemeyer.
As the Japanese retreated, the Chinese moved slowly forward in their wake. To the north-east of Chungking, the Chinese armies skirmished with the Japanese in June and July and then withdrew to reorganise when it became clear that the Japanese were prepared to hold their new defensive line in strength. In central and southern China the fighter was of a lesser nature, but the Japanese troop movements into northern and central China were largely unopposed, at least initially. Along the coast between Shanghai and Canton, Chinese Nationalist forces moved into Fukien province, and took the port of Foochow in May. Despite this success, the Japanese tightened their grip on Shanghai and, to the south of Foochow, also on Canton by reinforcing the garrisons of the two ports with troops withdrawn from Fukien and by sending additional troops to the Swatow and Amoy coastal areas between the areas of Canton and Hong Kong and of Foochow. Although they fully intended to reserve their main strength for the defensive struggle in the north, the Japanese meant to conduct a strong rearguard action against any Allied attempts to seize the southern coast from either the land or the sea.
On 26 June the Chinese recaptured the airfield at Liuchow, but severe fighting followed as the Chinese attempted to cut the Japanese line of withdrawal near Kweilin, on the railway about 100 miles (160 km) to the north of Liuchow. By the end of July, the Chinese had concentrated sufficient troops in the area for an attack but, after pulling back most of their strength to the north, the Japanese abandoned the city. By the beginning of August, therefore, the Japanese had almost completed their redeployment into the areas they intended to defend to the last.
Planning for the capture of Fort Bayard proceeded even as the Chinese followed the retreating Japanese. At a conference on Guam in the Mariana islands group on 6 August, representatives of the China and the Pacific theatres met to finalise their arrangements for the seizure of the area. At the time, Allied analysts estimated that the Japanese had more than 14,000 troops in the area, but in fact there were fewer than 2,000, and even those were in the process of withdrawing toward Canton. Nevertheless, a sharp action occurred on 3 August, about 20 miles (32 km) to the west of Fort Bayard, as the Chinese approached the city. The combination of this and poor weather, which limited air resupply, prevented the Nationalist Chinese troops short of reaching the coast.
The rest of 'Carbonado' was then rendered unnecessary by the Japanese surrender following US 'Silverplate' and 'Centerboard' atomic bombings of Hiroshima and Nagasaki on 6 and 9 August respectively, and the start of the Soviet 'Avgust Burii' invasion of Manchukuo on 8 August.