This is why I've started to dislike revisionist history. The premise that the threat of Stalin alone forced Japanese surrender is at least as ludicrous as saying that the nuclear bombs alone forced Japan to surrender.

I closed the page immediately because of the full-page popup ad, but I've encountered the premise elsewhere so it warrants examination.

The first thing to realize is that for Japan, whatever else happened an invasion of any sort would be harshly contested. It's not simply a matter of manpower either, there was a lot that was needed to be able to provide a workable invasion:

* Control of the air.

* Gunfire/artillery support to suppress the defenders prior to the assault wave.

* Logistical support, including landing craft (LOTS of landing craft), means of turning a beachhead into a supply terminal.

* More importantly for logistical support, a working supply chain to feed materiel to the battleground.

In almost all military aspects the U.S. was already in much better shape to host an assault on Japan. Even assuming the U.S.S.R. could pull all their troops from the occupation of Eastern Europe fast enough via the Trans-Siberian railroad they still would have needed to accumulate sufficient landing craft, field Naval support assets, build more airstrips and air bases, etc. etc. etc. As a side note, the whole reason Stalin would have needed to move the masses of troops back to the east was because he knew from his diplomats in Japan that Japan would respect the ceasefire that had been signed after Gen. Zhukov decisively defeated the Kwantung Army at the Battle of Khalkhin Gol in 1939, a military result that may have proven invaluable in the later defense of Moscow.

The Soviet troops fighting in Manchuria/Manchukuo in 1945 were in a much better military situation by comparison: The Kwantung Army's best troops had been continually bled to fight on the real front lines, Mao and Kai-Shek's guerrilla armies represented a constant drain on the Kwantung Army, and years of garrison duty had the effect of further reducing the martial ability of the KA compared to battle-hardened Soviet troops arriving from the Eastern Front.

But at this time the Soviet gains were achieved only overland. In fact the Soviets proved unable due to logistical difficulties to completely overrun Korea, a failure which would itself significantly alter the course of later history.

Sometimes proponents of the "Soviet shock" theory mention that it was the threat of attack on the Japanese Home Island from the undefended north which truly drove the spectre of fear amongst the Japanese leadership, but that's missing a very big point: There's a reason the Japanese defenders on the Home Islands were concentrating on the south! The Japanese could certainly have redeployed to the north if they had wished, so it seems that they feared the imminent U.S. invasion more than the potential threat of Soviet invasion.

But the Japanese knew the Soviets were going to attack. They in fact had been re-deploying the Kwantung Army to east Manchuria where they expected the attack to fall. The Soviets surprised the Japanese by attacking from every possible direction instead, but the surprise wasn't that the Soviets attacked at all, it was that it came sooner than expected and from the wrong directions.

None of this is to say that the atom bombs were the reason that the Japanese surrendered either. But it bears repeating that the Japanese were quite willing to fight an invasion of the Home Islands. Whether the invaders were American or Soviet was relatively immaterial, and given the massive American advantage in both air cover and Naval support the Americans could have invaded into a weak spot if that were the only concern.

In the actual event the news of the Nagasaki bombing had come during a Supreme Council being hosted by Emperor Hirohito amongst his closest advisers. The news drove the Council to split evenly on whether to surrender (but maintain the Kokutai) or surrender with further conditions.

An American B-29 pilot was tortured into "confessing" that the U.S. had a 100 more atom bombs, which would be used in the next few days, news which was used by Japan's War Minister to push for surrender. Likewise, when Emperor Hirohito broke his Council's tie (in favor of surrender) he explicitly mentioned the destructiveness of the atom bomb. One of the emperor's advisers even mentioned the 'twin shocks' of Soviet invasion and the atom bombs as being gifts in a sense, as it meant the Emperor could say he was forced to surrender and not that Japan "gave up".

So it seems clear that the Soviet invasion was core to the decision-making, but not that it was the only concern, and certainly not that the atom bomb was not factored in at all.