Tokyo knew about Soviet agreement to intervene against Japan
Yuriko Onodera's memoirs were published in 1985. Yuriko was married to Lt. Col. Onodera, an intelligence officer who worked at the Japanese Ground Forces General Headquarters. During the war, Yuriko traveled abroad with her husband, in particular, to Scandinavia, where she worked as a cryptographer and was privy to classified information. In her book she says that shortly after the Yalta conference, a London-based agent, a Pole by nationality, who was working under the pseudonym Ivanov, reported that the Big Three had agreed that the Soviet Union would enter the war against Japan. Onodera recalls: "I encoded this message with a heavy heart, and then sent it to Tokyo."
It is possible that the Japanese leadership obtained this information even earlier, immediately after the end of the Yalta conference. It can hardly be a coincidence that on February 14, 1945, that is two days after the end of the conference, the influential Japanese politician Prince Fumimaro Konoye, three times Japanese Premier, rushed a classified report to Emperor Hiro Hito, which urged him to "end the war as soon as possible." With undisguised concern, he said the main reason why the emperor should make this decision was the threat of "Soviet intervention."
Konoye wrote: "Regrettably, it seems to me that our defeat in the war is inevitable... Although defeat will certainly damage our national political system... a military defeat alone will not pose a particular threat to the very existence of our state system. In this regard, the biggest concern is not so much losing the war, as it is the Communist revolution that could follow in its wake."
"Having analyzed the situation, I have come to the conclusion that both the domestic and international situation are rapidly moving our country toward a Communist revolution. Externally, this is manifest in the unusual activity of the Soviet Union... Although formally the Soviet Union advocates non-interference in the domestic affairs of the European countries, in reality it is interfering most actively in their internal affairs and is trying to gain mass political support for the Soviet model. The Soviet intentions in East Asia are just the same... There is a real danger that the Soviet Union could interfere in Japan's internal affairs in the near future."