Blood for oil...
Japan at War: 1936-1976
"If the arguments in Britain were bitter, they lacked the hatred found in Japan. The ultra-nationalists decried siding with a power in decline, which still maintained colonies in Japan's rightful sphere."
"However, Yonai proved adept at maneuvering against the various factions. Since the Emperor had entertained the proposal, no one could criticize it directly. There were still memories of Britain and the alliance of 1902, the perception that perhaps Britain was a friend of Japan's. The Army, for their part, also grudgingly admitted it would help end the war in China. Thus, their threats to bring down the government proved empty. Yonai's ploy to have the British offer via Shigemitsu was brilliant, as well as having the burden (American outrage) of militarizing Hiei (actually already done by now in secret)."
"The terms of the Treaty stipulated that if the USSR attacked Japan, the UK would declare war as well. If war broke out between Japan and the US, Britain would be free of all obligations. This part was to be secret, but the British could "leak" it to the Americans. Japan would keep a minimum of 30% of her fleet at Britain's disposal; tonnage determined by war needs. Japanese ships were commanded by her officers up to flag level, but Britain was in overall command of the joint fleets [Britain did not trust Japan to operate her own fleets, and strove to keep any mixed fleet 60% British]. Another secret provision was that Britain would end all aid to China, and pressure Chiang Kai-Shek into accepting peace terms; the Japanese were desperate enough to not force reparations and were even willing to pull back some, remaining on Hainan and still getting her puppets Wang Jingwei and Manchukuo, and a 3 year withdrawal from the coastal regions (goal of 2; this would allow the Japanese to proclaim they were leaving early on their own)."
"What is significant is what was not included. No technology transfer (the British did provide higher octane fuel to ensure higher performance); Japan struggled to develop her own radar, for example. The Japanese merchant marine were almost completely devoted to British needs; on the return trip laden with rubber, metals, and oil (all bought at war inflated prices). Japan financed these purchases with a mix of loans and payments (from the use of the fleets and merchant ships). This was not a friendship; it was a marriage of convenience."
"The benefits to Britain were significant. The heavy losses of merchant ships in the summer of 1940 were partially offset by the Japanese, allowing for much of Britain's naval building program to continue. Paying the Japanese in pounds (and charging war prices!) allowed her currency reserves, particularly dollars, to stabilize. Britain still bought weapons from the US, as Japan was felt to produce inferior products [although modifying to British standards would have costly]. Manchurian iron ore was even shipped, lessening British needs on America."
Late at night, May 1940
Yonai had ensured Japan would not join the Axis, and already merchant ships were moving supplies to the British Empire. But now it was time to send the Fleet, while leaving enough strength against any possible surprise American attack. He looked at the list, musing. Yamamoto: widely respected, talented, and pro [Naval] Treaty... unfortunately, too valuable to send away yet. Reasonable men were hard to find in government, and Yonai had none to spare. Nagumo was decent, not exceptional, but would not lose the fleet recklessly, and had the necessary rank. Who else... Yamaguchi was a hot head, but Ozawa showed much promise. The British wanted 2 fleets, one in Scapa Flow, the other at Gibraltar. Nagato, Mutsu, Kaga, Akagi, all four of the Mogami class (at British request, since 8-inch cruisers were valuable), plus destroyers. Nagumo in charge, Yamaguchi as well. Ozawa would get Hiryu, Kongo, Haruna, probably no cruisers or destroyers. He was already weakening the Home Islands defense. Ryujo and Soryu could shuttle aircraft as needed. They were rapidly mobilizing; he hoped to get them in place by the end of June. His work done, he quietly got ready for home.