The Persimmon Had a Calendar

A question on r/AskHistorians this week asked why Japan put a million men on the Soviet border in 1941 and never used them. The standard answers are oil, the China quagmire, and the Army–Navy budget fight, and they are good answers. One commenter mentioned a detail that interests me more: the War Ministry had set August 10 as its deadline for deciding on war with the USSR. If you work out where that date came from, the plan stops looking like a choice between two strategies. It looks like a machine with two dials that could never both read “go” at the same time. The first dial was the weather. Fighting in the Soviet Maritime Province had to be over by mid-October, before the Siberian winter stopped operations, and the General Staff counted backwards from there (Kantokuen, citing Coox, Nomonhan, p. 1038). That gave 35 days of fighting before the frost, preceded by 31 days to concentrate troops, preceded by a decision. The decision date fell 49 days after Barbarossa began. Nobody picked August 10 because it was a good day to decide. It was the frost date minus the length of the operation minus the time needed to move the troops.

The second dial was the “persimmon”. In the internal debate the idea was that you don’t climb the tree, you wait for the fruit to ripen and fall. The planners made this numerical: Japan would attack once the Soviets, rushing forces west, had cut their Far Eastern infantry by half and their armour and aircraft by two-thirds. On 1 June 1941 the Far Eastern Front and Trans-Baikal District held about 650,700 men, 5,400 tanks and 3,021 aircraft. By 1 December, after the worst months of the Moscow crisis, they had sent west 122,000 men, 2,209 tanks and roughly 1,800 aircraft (the aircraft figure is a Japanese estimate). That is a drop of 18.7%, 40.9% and 59.6% (Glantz; Coox p. 1055). Even by December the manpower condition was less than halfway met. On August 10, the only day the timetable allowed a yes, the Japanese official history describes the westward transfers as still “relatively small in scale” (関東軍特種演習; Senshi Sōsho vol. 73). The deadline was set by the season. The trigger was set by how Stalin paced his transfers, and he had no reason to empty the Far East in seven weeks.

You can watch the calendar squeeze the plan through the summer. The first phase was budgeted at 6–8 weeks, then at 35 days, and later drafts claimed the Maritime Province could be overrun “in 21 days.” No new intelligence produced that estimate. It is what happens when the frost date stays fixed and the start date keeps slipping. The US oil embargo of 1 August settled the matter, and the General Staff gave way on 9 August, one day before its own deadline. By then 463,000 reinforcements had already arrived, which brought Manchuria to 763,000 men. The plan was finished, but the men stayed. Seen from Moscow, the same clock ran the other way. Once mid-August passed without an attack, winter would protect the Soviet Far East until the thaw no matter what Tokyo intended. Kwantung Army hawks found this out in the autumn, when they had to pull troops back from a frontier with no winter billets.

That suggests the Soviet transfers should follow the calendar rather than the spy reports, and the available record fits. A compilation of division histories (operationbarbarossa.net) shows Far Eastern formations leaving mostly in September–November. Only three divisions are listed for July. The 78th Rifle needed 36 trains and ten days to reach Istra in late October (Gorbunov & Kretov 2013). Richard Sorge’s famous cable reporting Japan’s southward turn is dated 23 August (nippon.com), two weeks after the Japanese decision, so it told Moscow something the season was already making true. A plan whose go-signal depends on the enemy’s behaviour, but whose deadline depends on the weather, hands the enemy a veto that costs nothing more than waiting. My bet is that a month-by-month archival series of Far Eastern Front strength would show the decline concentrated in October–December 1941, after the Japanese window had closed, with tanks and aircraft cut well ahead of men. Moscow would have stripped the scarce items and kept the cheap one, because headcount was the number Tokyo was watching. One caveat: the by-month division list is a secondary compilation, and it dates when units were assigned, not when they boarded trains. That is the test I would want run.