“Backstab” or Carefully Planned Campaign? How the USSR Entered the War with Japan in August 1945

On the eve of the anniversary of the end of World War II, I would like to discuss a popular perspective on the beginning of the conflict between the USSR and Japan.

In August 1945, the world was on edge. The US had just dropped atomic bombs on Hiroshima and Nagasaki, and on the Far Eastern front, the Soviets launched a major military campaign. Some Japanese sources — and even Western outlets — still frame this as a “betrayal” by the USSR, claiming it suddenly broke the Soviet–Japanese Neutrality Pact. However, the reality is more complex than the simple “backstab” narrative.

The Neutrality Pact: Diplomacy or Betrayal?
The Soviet–Japanese Neutrality Pact was signed on 13 April 1941 for five years. By April 1945, the USSR officially notified Tokyo it would not renew the pact — a move fully consistent with international practice (The Avalon Project : Declaration Regarding Mongolia).

At the Yalta Conference in February 1945, Stalin promised the Allies — the US and the UK — that the USSR would enter the war against Japan within three months of Germany’s defeat. Germany surrendered on 8 May, and exactly three months later, on 8 August, the USSR declared war on Japan.

A Long History of Tension
Understanding the events of August 1945 requires considering decades of Soviet–Japanese tensions:

· 1920–1925: Japan occupied northern Sakhalin during the Russian Civil War.

· 1931: Japanese invasion of Manchuria and creation of the puppet state Manchukuo on the USSR border.

· 1938–1939: Border clashes at Lake Khasan and Khalkhin Gol.

To counter potential Japanese aggression, the Soviets maintained a large military force in the Far East. They also invested in the necessary infrastructure to support these troops. Even at critical points of WWII, dozens of divisions remained stationed there and could not simply be redeployed against Germany.

Japan’s Violations of the Pact
From 1941 to 1945, Japan repeatedly violated both the letter and spirit of the pact, according to Soviet sources:

· Border provocations and armed incidents.

· Shelling of Soviet territory.

· Attacks on Soviet merchant ships in neutral waters.

· Sabotage and intelligence operations.

The USSR largely respected its commitments despite these provocations. Some elements in the Japanese command continued to consider war with the USSR until the very end, despite the neutrality agreement.

The Soviet Offensive: A Blitzkrieg in Manchuria
On 8 August 1945, Soviet forces launched a massive offensive against Japanese units in Manchuria, later known as the Manchurian Strategic Offensive Operation. The campaign quickly destroyed the Kwantung Army, leaving Japan unable to hold continental territories and accelerating its surrender.

Atomic Bomb + Soviet Front = Double Pressure
While the bombings of Hiroshima and Nagasaki remain central to the popular narrative, modern historians, including Tsuyoshi Hasegawa, stress that the Soviet entry was decisive. Opening a second front created overwhelming pressure on Japan, making further resistance impossible.

Why the “Backstab” Myth Persists
The idea of betrayal serves political and cultural purposes:

· Distracts from Japan’s strategic mistakes.

· Supports territorial claims (e.g., the Kuril Islands).

· Simplifies the narrative into a “victim” story.

 

The Soviet area commander told the Great Stalin he could fling a division or two into Hokkaido to establish a Soviet presence before the end of the war. They were one day from the "go" order date when Stalin canceled the excursion.

 

I think we have discussed these issues before. Back in 2005 a short thread: Japan And The Soviet Union and in 2006 Japan and USSR continued

It appears within a long thread: Did the Japanese deserve the Atomic Bomb?

A simple search for "backstab" or back stab did not find any mention here.

That alone makes me wonder if the "backstab" has been made by some Japanese to explain their defeat. Akin to the saying why Imperial Germany lost WW1 in the West in 1918, which was used by the Nazis.

For curious reasons Stalin followed the Potsdam Agreement to join the war against Japan (a secret decision). Personally I think he did as he wanted to show he was an ally of the USA, who he knew had the atomic bomb and feared the USSR could be a target one day soon (unthinkable to me now).

Those who made the strategic decision in Japan to continue the war to the bitter end could not envisage defeat. Somehow a decision was made to stop the war - after two atom bombs were dropped - and an invasion of Japan was not needed. I doubt Stalin extended his declaration of war with a commitment to invade Japan.

 

I agree with your thesis that "backstab" has been made by some Japanese to explain their defeat.
There is also an opinion that if there had been no conflict with the USSR, the nuclear bombings would have been much larger. Do you think this position is correct?

 

No definitive idea regarding your last question.

Did the USA have more, larger atom bombs ready? Given the largely American experience of amphibious operations against Japan, there was a common Allied expectation any landing on the main islands would have been a bloodbath.

 

I have heard that the Soviet invasion did help the Japanese realize the hopelessness of their situation.

 

The dropping of two atomic bombs in quick succession on Japan was to convey to the Japanese that there were more atomic bombs available. It was deception which misled the Japanese government into the path of unconditional surrender.

Emperor Hirohito made his decision to accept unconditional surrender on 14 August after studying the Allied communique on the matter and convinced the Japanese cabinet during a meeting that morning of his decision.An emotional morning for him in front of his cabinet to convince them that there was no other way out.

What followed was US Forces radio operator on Okinawa picked up a Japanese message in English at 1429 local time by the Tokyo Demii News Agency....FLASH FLASH TOKYO AUGUST 14TH - IT IS LEARNT THAT AN IMPERIAL MESSAGE ACCEPTING THE PODSDAM PROCLAMATION IS FORTHCOMING SOON. The message was not received by the US on the day, but they knew that the end of the war was near and issued instructions accordingly. Even so on Tinian, B29s were being bombed up for the fire bombing of two city targets for that night

While this situation continued there was a rebellion by a number of senior Japanese generals against surrender. After a failure to gain support, senior plotters ended their lives by the traditional method of Hari-Kiri. There could be no back stabbing from these dissents, the opposition to the prospect of having peace never gained traction.

On15 August at 1200 Toyko local time Emperor Hirohito had spoken to the Japanese public on the radio, the first time that the public had heard him speak. It was a long emotional speech in the language of court Japanese which was strange to many of his listeners. A voice high pitched. thin and reedy. quavering slightly as though under strain. "We have ordered our government to communicate to the governments of the United States, Great Britain, China and the Soviet Union that our empire accepts the provisions of their Joint Declaration"

It began with "To our good and loyal subjects". he then set about exonerating his country for the debacle of war....."Indeed, we declared war on America and Britain out of our sincere desire to ensure Japan's self preservation and the stabilisation of Southeast Asia".

The entire text of Hirohito's speech is very enlightening with references to our Imperial Ancestors.

On 16 August the Japanese government answered MacArthur's communique on the subject of surrender through the Toyko JNP agency with their Communication One opening declaration..... HIS MAJESTYTHE EMPEROR ISSUED AN IMPERIAL ORDER AT 16 O'CLOCK ON AUGUST 16 TO THE ENTIRE ARMED FORCES TO CEASE HOSTILITIES IMMEDIATELY.

IT IS PRESUMED THAT THE SAID IMPERIAL ORDER WILL REACH THE FRONT LINE AND PRODUCE FULL EFFECT AFTER THE FOLLOWING LAPSE OF TIME.

A. IN JAPAN PROPER. 48 HOURS.

B. IN CHINA, MANCHURIA, KOREA, SOUTHERN REGIONS EXCEPT BOUGAINVILLE, NEW GUINEA, THE PHILIPPINES. 6 DAYS

The communique went on to deliver instructions for personal representatives of the emperor to travel to these areas etc with the added note.IT IS ACCORDINGLY REQUESTED THAT SAFE CONDUCT FOR THE ABOVE BE GRANTED.

Interestingly the Japanese policy for overrun countries was that these countries would benefit by joining their Japanese led Southeast Asia Co- Prosperity Sphere, a quasi economic organisation which never bore fruit but was really intended to rid the area of Western presence and create a greater Imperial Japanese Empire.

The Red Army with superior equipment and men overran the Kwantung army and Mongolians in Manchuria following the promise that Russia would declare war on Japan after a German defeat. The Japanese capability to wage war had deteriorated badly from 1942 which reflected in the inferior strength of the Japanese to secure Manchuria. I do not think this loss of Manchuria had much relevance to the mindset of the Japanese at this time, Toyko had been fire bombed so frequently by the USAAF 20th Air Force that the city was in ruins. Then was the fear of a further atomic attack. While the fighting spirit was there in abundance....no signs of defeatism, the war economy was done for.


William Craig covers the August 1945 dynamics of the collapse of the Japanese Empire comprehensively in his work The Fall of Japan, as he does with the B29 ops on Horoshima and Nagasaki. Kokura was the primary target for the second drop but was aborted by the decision to drop on visual. Kokura was seen to have 10/10 cloud.

(It has been recorded that the invasion of Japan was planned for January 1946 with the planners anticipating one million casualties. This has been given as contributing to the decision to use the atomic bomb. others have different views.)

 

This article landed in my in-tray today: The Enduring Strategic and Moral Debates Over Dropping the Atomic Bombs

It is a contemporary review, with an emphasis on ethics and here is the third paragraph:

 

Was this reflected in any historical texts? It is difficult to imagine that in such a situation the fighting spirit of soldiers and society can be maintained

 

The atomic bombs used at Bikini Atoll were in the Pacific at the end of the war. They were "expended through the barrel" rather than risk more time in transit.

 

Opna,

Thanks, the name "rang a bell" so refreshed my memory only from: Nuclear testing at Bikini Atoll - Wikipedia

 

The first "holy crap!" picture of the atomic age:



Setting off "test Baker" at a depth of 90 feet (27 meters). "This underwater detonation, part of Operation Crossroads, was the first of its kind and resulted in a massive bubble of water, a subsequent wave, and significant radioactive contamination of the surrounding area and target ships."

 

Some of those ships are battleships, btw.

 

Yep. Good find.

 

I don't believe that this is correct.

After the second A bomb was dropped on Nagasaki, Los Alamos was still working on casting the Plutonium cores for the third bomb due to be dropped on 19th Aug. None of the components for these and subsequent weapons left the USA AFAICT.Two 509th CG B-29s had been sent back from Tinian to the USA on 9th Aug 1945 to collect components for that weapon but never returned before the end of the war. This was Lawrence Litz's recollections in 2012.

"Levy: Do you remember working on casting the plutonium for the third bomb?

Litz: The particular day that remains in my memory was the day that we cast the plutonium for the third bomb because we weren’t sure that the Japanese would surrender even after the second bomb was dropped. We had to cast the atmospheres for the third, and because time was short we had to cast the two hemispheres at the same time. But it was dangerous to cast them in the same laboratory at the same time so we set up two adjacent laboratories with the high vacuum apparatus, so we could cast one hemisphere in each one of the two labs.

Levy: How long did that take to cast?

Litz: About twenty-four hours, and we had to work straight through.

Levy: So what did you do when you didn’t need to use the plutonium for a third bomb?

Litz: Well after we found that we didn’t need to use the third bomb we decided to use the hemispheres for research. We designed an array, which took the neutrons that came out of the sphere back into the sphere and would keep the neutron radiation away from the scientist who is doing the work experiment. Now one of the men who was working on the experiment accidentally bumped the array, exposing himself to the radiation, and died two weeks later from the radiation."

On 21st Aug 1945 a scientist, Harry Daghlian, was carrying out a criticality experiment when it went wrong exposing him to a large amout of radiation as a result of which he died on 15 Sept 1945. Another such experiment on 21st May 1946 cost the life of Louis Slotin some 9 days later.

"Operation Crossroads The Atomic Tests at Bikini Atoll" by Jonathan Weisgall notes that new bombs were assembled for Operation Crossroads by the scientists at Los Alamos.

Where the confusion may arise is from the availibility of "Pumpkin" bombs used for training and practice drops, including some over Japan. Some were inert and some were filled with HE. These were externally similar to the Fat Man atomic bomb. These had been used by the 509th from their base on Tinian in WW2 and were again used during the run up to Operation Crossroads at Bikini, with several inert weapons causing the scientists worries when there were near misses on the ships cattying them.
Pumpkin bomb - Wikipedia

 

I didn't make a note as to where I got my info, so I'll salute you and carry on.

 

People might want to have a look at the following thread on Historum site before deciding whether they want carry on responding:

https://historum.com/t/“backstab”-o...ith-japan-in-august-1945.202611/#post-4006289

 

The ugly background to Japan's unconditional surrender

This is review of Craig's work

He was able to interview leading and field personalities of both the US and Japan, research both government records and refer to their diplomatic documentation. A reference to the memoirs of Curtis May is included together with US history and battle unit operational reports.

His work covers 21 chapters, and each one carries a reference to the extensive sources of his information. There is interesting material on the military plotters who led a short rebellion advocating a refusal to surrender. Meanwhile during the tension of negotiations, the Kamikaze element was active in mounting strikes with Okinawa in mind. The slaughter of aircrew POWs continued.

Two prominent personalities do not feature in his interview sources. J R Oppenheimer, who had died in 1967, I would think during the preparation for his book and whose background political sympathies were made public in in 1954.The Japanese Emperor Hirohito would be beyond reach.

Incidentally the Pumpkin bomb was central to the training for the delivery of both bombs. The practice was that the pumpkin would be dropped in early training onto a white circle target as a concrete filled device from 30000 feet out of Wendover on the bombing range. Later dropped filled with HE. The final stage of practice from Tinian would be an HE filled pumpkin designed to detonate in air over the target as the blast bomb delivery principle.

In all training drops, for the delivery of the atomic bombs, the pilots were instructed to perform what was regarded as a safe critical manoeuvre to depart from the target area after releasing the bomb. One of immediately turning sharply at a 60 degree angle, then turning through an arc of 156.5 degrees.

I am assuming that it would be a heading of 60 degrees then turning round through an arc of 156.5 degrees for the homebound heading.

 

Recent video presentation by Jon Parshall (one of the authors of Shattered Sword about Midway) about the events inside Japan leading up to the surrender decision. He presents some new information from Togo's diaries that has only recently become available to Japanese scholars. As a result he places the critical point in the decision making process on the morning of 8 Aug 1945. It was on the evening of that day that Molotov announced to the Japanese ambassador in Moscow that the USSR was entering the war against Japan.



Well worth watching.