General Maltby was not the only man to have the defences of Hong Kong on his mind. They also figured prominently in the thoughts of Lieutenant General Sakai, who commanded the Japanese 23rd Army, and Lieutenant General Sano Tadayoshi, commanding the 38th Division in that army.
Japanese preparations for the capture of Hong Kong had been in hand for some time. The freezing of Japanese funds in the United Kingdom, United States, and Netherlands East Indies in July 1941, soon began to hurt Japan, and by the fall Imperial General Headquarters had commenced preparations for war. The Tojo government confirmed this policy and on 5 November 1941, decided to definitely go to war if negotiations with the United States had not succeeded by 25 November. Orders were sent to Imperial General Headquarters to have operational planning completed by the end of November.
The Japanese had always maintained a close watch on the state of the Hong Kong defences. In September 1941, the Japanese General Staff estimated that the Hong Kong garrison consisted of 13,500 regular troops plus 5,500 volunteers. This estimate, made before the arrival of the Canadians, was over 50% too high. The General Staff estimate of the air and naval strength was more realistic -they credited the air force with ten training aircraft and the navy with three destroyers and 33 other vessels.
On 6 November 1941, the Japanese Imperial General Headquarters ordered its Commander-in-Chief, China, to prepare plans for the capture of Hong Kong. He was instructed that the 38th Division of the 23rd Army was to form the core of the force and that all preparations were to be completed by the end of November. He was also informed that the attack on Hong Kong was not to imperil the areas of China already occupied and that therefore the remainder of the 23rd Army would deploy to protect the rear of the assault force in the unlikely event of Chinese intervention. Operations against Hong Kong were to commence as soon as word was received of the Japanese landing in Malaya.
The plan of attack prepared by Lieutenant Generals Sakai and Sano was an uncomplicated one, with a straightforward basic design which demonstrated a typical Japanese flexibility and willingness to exploit the favourable aspects of a situation as they developed. Before the ground attack commenced, the enemy air and naval forces were to be neutralized by bombing. The Japanese were well aware of the reactivation of the Gin Drinkers Line and expected that the main military resistance would be encountered there. Their intention was simply to cross the border, advance to the Line, and launch a full-scale attack. If necessary the navy could be called in to transport troops in a flanking movement. After the Gin Drinkers Line had been passed, the mainland would be completely occupied and installations on outlying islands eliminated. The Island of Hong Kong itself was then to be invaded and captured. The Japanese troops were to land and form a beach-head on the north shore and simply enlarge their gains from there.
If the Japanese really believed their September estimate of the strength of the Hong Kong garrison, they showed considerable confidence as they only allotted a single division, albeit a heavily reinforced and supported one, to the capture of the colony.
In overall command of the operation was Lieutenant General Sakai, who was to control all elements of the operation, including those detailed for the rearguard. The 23rd Army (which in Western parlance would have been designated a Corps), had been operating in the Canton area of South China for some time. In December 1941, it consisted of four divisions plus a mixed brigade and two infantry regiments.
The actual attacking force was known in the Japanese fashion as the Sano Force after Lieutenant General Sano Tadayoshi, who commanded the 38th Division. The infantry component of this division (38th Infantry Group) was commanded by Major General Ito Takeo and consisted of three regiments of three battalions each. They were the 228th under Colonel Doi, the 229th under Colonel Tanaka, and the 230th under Colonel Shoji. The remainder of the division was under the direct control of Lieutenant General Sano and included a Light Armoured Car Unit with ten cars, the 38th Mountain Artillery Regiment of three battalions, the 38th Engineering Regiment, the 38th Transport Regiment, and Signal, Ordnance, Veterinary, and Medical Units plus two Field Hospitals.
Attached to this already formidable basic division were two Independent Mountain Artillery Regiments, the 10th and 20th, two Independant Anti-Tank Gun Battalions, the 2nd and 5th, the 21st Mortar Battalion, the 20th Independent Engineering Regiment, three Transport Regiments plus 3 companies of another, and two River Crossing Companies. These units greatly augmented the fire support, transport, and engineering capabilities of the 38th Division and made it even more suited for its assault role, Supporting the 38th Division's own and attached artillery was the entire Army artillery of the 23rd Army which included a Siege Unit with a regiment of 150-mm howitzers plus two independent battalions equipped with 9.4-inch howitzers.
Strong air support was available. Acting directly in conjunction with the 23rd Army was a light bomber regiment with about 40 Kawasaki Ki.32 single-engined bombers. After December 16, a heavy bomber regiment of 18 aircraft was also available to support the attacking forces. "Popular" historians automatically assume that the formidable Zero naval fighters were operating over Hong Kong. This was not the case, as it was purely an army operation and no fighters of any type were employed- they were unnecessary.
The supply of the Sano Force and the protection of its rear was undertaken by various groups-the Kitazawa, Kobayashi, Sato, and Araki units, all named after their commanders. The Araki Unit, of approximately brigade strength, was the one specifically detailed to prevent any interference with Sano Force.
Sano Force was definitely a formation to be reckoned with. That such an aggregate of military strength could be spared from the Japanese forces in China without any apparent difficulty, implies a very serious underestimation on the part of the British Intelligence, whose reports implied that the Japanese were too occupied in China to be able to attack Hong Kong, to say nothing of being able to make troops available for invading Malaya and the Philippines. Sano Force was distinctly superior to Maltby's Hong Kong garrison, particularly in mobile artillery. The numerical superiority of the cutting edge of the division, the infantry, was not as marked -nine Japanese battalions against six British, Canadian, and Indian battalions, plus at least a battalion and a half of Volunteers. However, the Japanese would be able to concentrate their strength, and if they could succeed in breaking through the outer defences, would be able to force battle on their own terms. In addition, the Japanese soldiers of Sano Force would obviously be formidable antagonists. While it is uncertain whether the 38th Division had participated in any pitched battles against the Chinese, its men had worked together in an operational environment for some time and were seasoned in anti-guerilla operations and security duties. Training of the Japanese soldier emphasized mobility in combat, coordination with other arms, the importance of close combat, individual initiative, particularly on the part of NCOs, and the importance of night combat.* In the case of the Sano Force men, this rigorous and thorough initial training had been augmented by the most valuable training aid of all -experience.
*When it is considered that Japanese training manuals and other information on training were available to the British and Americans, their persistence in cultivating the myth that the Japanese lacked initiative and were poor at night work is hard to understand.
It was this well-equipped, fit, and experienced force that in early December was moving unobserved along routes to the Hong Kong border, which they would cross on 8 December to do battle with Maltby's ill-trained, polyglot garrison.