The last few weeks of the Pacific War saw several dramas played out simultaneously. On 16 July 1945, the day before the allied leaders met at Potsdam, the successful atomic test gave President Truman a prospect of achieving Japan’s surrender without Soviet participation. A race began, between Stalin’s desire to keep Japan in the war till he was ready to attack it, and Truman’s wish to postpone its surrender only till atomic bombs were ready.

Truman narrowly won the race; the first bomb was dropped on 6 August, the Soviet Union declared war on the 8th. But contrary to American expectations and post-war claims, the author’s diligent research in the Japanese sources demonstrates conclusively that it was the Soviet declaration of war, not the atomic bombs, that forced the Japanese to surrender unconditionally. It undermined the positions of both main factions in the leadership, each of which needed Soviet neutrality, those favouring conditional surrender because they hoped for Soviet mediation, and those wanting to fight on, because the attack ended their slim prospects of fighting to a negotiated peace.

Overall this is a masterly treatment of several complex and rapidly changing sets of relationships, with the Cold War not yet born, but in gestation, the evidence cited showing American concern at the extent of the Soviet gains in Asia, Soviet aspirations to an occupation zone in Hokkaido, and Japanese hard-liners’ hopes, only slightly premature, of exploiting differences between the Soviets and Anglo-Americans to Japan’s advantage.

However, on a few minor points one may take issue with the author. He perhaps links realisation of Stalin’s territorial ambitions more closely to attacking Japan before it surrendered than the facts warrant. The territories he took had been promised at Yalta, and would be more easily and quickly seized if Japan had already surrendered, but then would be gifts conferred by American military prowess, not Stalin’s strategic ‘genius’. Most of his ‘price’ for joining the war against Japan was recovery of all Russia lost through defeat in the Russo-Japanese War of 1904–5 – in China a naval base (Port Arthur), commercial port (Dairen), the South Manchurian Railway (also the Chinese Eastern Railway, sold to Japan in 1935), and South Sakhalin, and adding the Kuril Islands. During meetings at the end of June 1945 to finalise preparations for the Far East campaign, he assumed the rank of Generalissimus, unknown in Russia since 1800, and in his victory speech on 2 September implicitly contrasted his success with Tsar Nicholas’ failure by saying the men of his generation had waited forty years for that day. It seems his motives were psychological as well as geopolitical.

Editorial laxity has transmogrified the one mention of Australia, in the list of signatories of the surrender document, into ‘Austria’. That is unfortunate, but even more so is the lack of mention of an event there that suggests Stalin was prepared to go even further than Professor Hasegawa indicates to join the war before Japan surrendered. In January 1945 a security scare in Australia followed American deciphering of a November 1944 message from Harbin to Imperial General Headquarters in Tokyo, containing details of Allied military plans, and giving the source as ‘Soviet Embassy Canberra’. The Soviet mission there (then a Legation) had no radio transmitter; its traffic could go only by courier or cable via Moscow, and Japan had not penetrated Soviet security there, so the information could only reach Harbin via Soviet channels. In Harbin the Soviet Consulate-General had no use for it, but Kwantung Army Intelligence had plenty. The least unlikely conclusion is that Moscow was passing information to help keep Japan in the war till Soviet forces could attack it, using Harbin so that it could blame any leakage on anti-Soviet elements in the city’s then large Russian population. General Yanagita, Head of Kwantung Army Intelligence, and his principal subordinates in Harbin, Dairen and Port Arthur were never repatriated. That tends to suggest awareness that if they returned to Japan their knowledge would present American debriefers with an embarrassing propaganda victory.

There is also perhaps excessive stress on Stalin’s alleged need for an excuse to violate the Japanese-Soviet Neutrality Pact. The Anglo-Americans had long sought the Soviet Union’s entry into the war against Japan, so they would not excoriate it for violating the Pact. Only the Japanese government would do that, and who then cared what it said?

However, these are minor flaws in a generally excellent work. Professor Hasegawa dedicates it to Dr Boris Slavinsky, who collaborated in its preparation but died before it was written. Having collaborated with Dr Slavinsky on another book he did not live to see, I agree that his death was a great loss to scholarship in the field of Russo-Japanese relations.