Questions about Operation Downfall

Did the Soviets have sufficient landing craft for the invasion of Hokkaido?

They probably could not have contemplated such a thing until after their main opposition in northeast Asia had been defeated, i.e, in 1946. Their Pacific Fleet's amphibious capacity had already taken a hit during the invasion of Shumshu and would have been insufficient to invade Hokkaido without additional support from the US and/or further landing vessels being brought in-theater.

Also could the Soviets have taken all of Korea?

Eventually they probably would have. The Soviet ammunition situation was tenuous, but the Japanese were even worse. The main Kwantung Army only had enough ammunition for 13 divisions to fight for 3 months; with 24+ divisions (albeit lightly armed) their real capacity for protracted warfare was likely much less. While the IJA in Korea had some halfway-decent divisions in the South plus the 17th Area Army in the North, even they were under-supplied given the demands of the Home Islands sucking up everything.

Assuming maximum Japanese resistance-how long would the campaign have lasted?

My guess is in the neighborhood of 4-6 months, maybe longer where South Korea and the Kuriles are concerned.

Would there have been a north Japan-south japan Cold War situation. With the US controlling the South and the Soviets holding Hokkaido and northern Honshu?

Soviet occupied Japan would have been confined to Hokkaido at most which is economically incomparable with the rest of the country; it wouldn't have been much of a Cold War.
 
NATO didn't exist during this time frame, so that is off the table.

There is no certainty that the Soviets would have invades any part of the Home Islands. It is possible, but the U.S. was in strong opposition and there were much easier pickings on the Asain mainland.

I agree with Carl on the book recommendation for the other facts & figures. There are other works, but for a fairly compact overview it is excellent.

The Russians didn't have that sort of amphibious capability. The Russians main military experience with amphib ops was desant ops using brigade sized forces against light opposition in places like the Black Sea and Norway.
 

CalBear

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The Russians didn't have that sort of amphibious capability. The Russians main military experience with amphib ops was desant ops using brigade sized forces against light opposition in places like the Black Sea and Norway.
They wouldn't have needed that much in the way of finesse. The Japanese had moved all their remaining aircraft to northern Kyushu and southern Honshu, along with all their armor, heavy artillery and just about all their remaining motor transport available on the Home Islands. What you had left on Hokkaido was a light brigade of leg infantry and militia (some with actual rifles, most with spears or satchel charges), with minimal beach defenses and absolutely no real hope of stopping a determined airborne attack at Otaru or elsewhere near Sapporo. Once the Soviets have somewhere they can dock transports, its over.

Only real question is how bad Stalin wants the Island and how willing he is to seriously piss off the U.S. when there are much richer picking to be picked up for a song on the Mainland.
 
They wouldn't have needed that much in the way of finesse. The Japanese had moved all their remaining aircraft to northern Kyushu and southern Honshu, along with all their armor, heavy artillery and just about all their remaining motor transport available on the Home Islands. What you had left on Hokkaido was a light brigade of leg infantry and militia (some with actual rifles, most with spears or satchel charges), with minimal beach defenses and absolutely no real hope of stopping a determined airborne attack at Otaru or elsewhere near Sapporo. Once the Soviets have somewhere they can dock transports, its over.

Only real question is how bad Stalin wants the Island and how willing he is to seriously piss off the U.S. when there are much richer picking to be picked up for a song on the Mainland.

The Japanese defenses on Hokkaido were centered around the elite 7th Division (a Type A division from the Kwantung Army specializing in Arctic Warfare), the 42nd Division (which was decent, a Type B division formed in 1943), the 101st Independent Mixed Brigade, and the 7th Armored Regiment. Additionally there were 454 aircraft of all types (101 fighters, 35 bombers, 131 recon, 151 transport, and 36 trainers), a considerable complement of Naval personnel, and a series of strongpoints sited at potential landing zones as shown below:

4g3imp.jpg

This would have been no cakewalk for any Red Army invasion, and likely would have required a concerted effort from everything they could muster to avoid being pocketed and Anzio'd. It honestly seems like another Sea Lion, hence my claim that it wouldn't have been feasible until 1946.
 

CalBear

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The Japanese defenses on Hokkaido were centered around the elite 7th Division (a Type A division from the Kwantung Army specializing in Arctic Warfare), the 42nd Division (which was decent, a Type B division formed in 1943), the 101st Independent Mixed Brigade, and the 7th Armored Regiment. Additionally there were 454 aircraft of all types (101 fighters, 35 bombers, 131 recon, 151 transport, and 36 trainers), a considerable complement of Naval personnel, and a series of strongpoints sited at potential landing zones as shown below:

4g3imp.jpg

This would have been no cakewalk for any Red Army invasion, and likely would have required a concerted effort from everything they could muster to avoid being pocketed and Anzio'd. It honestly seems like another Sea Lion, hence my claim that it wouldn't have been feasible until 1946.
The defenses were, but were the troops still there, and were they still the elite forces that had existed? Were the aircraft still there? Was there still fuel for the aircraft there, how many of them could still fly (assuming there was fuel)?

The Seventh Division had already lost one Regiment of its best troops at Tenaru River and Edison's Ridge thanks to Colonel Ichiki's ill-advised attacks while in command of the 28th Regiment. Additional troops had been bled off for different missions (including the invasion and garrisoning of Attu), replaced by late war conscripts of much lower quality.

Moreover the 42nd was concentrated on the northwestern tip of the Island near Wakkanai in defensive positions lacking transportation some 150 miles from the Sapporo Bay region. The 7th Division was concentrated to the southeast, generally in the area of Obihiro, over 100 miles from the Sapporo area. Even today that is a difficult trek, especially if most of the troops need to move by foot. The defensive position shown near Sapporo are 32 miles apart, incapable of mutual support.

Certainly the force that are still in place (and considering the way the Japanese were bleeding troops, the difference between paper strength and actual ration strength is likely to be significant) will fight to the best of their abilities and extract a considerable toll, maybe even one that would lead an American or British planning staff to reconsider. We, however, are not talking about the WAllies, we are talking about the Red Army and Stalin, both of which were effectively numb to casualties at this point. As I have noted previously, it is probable that the Soviets would see far more value in areas like the Korean Peninsula and Manchuria which are there for the taking without causing friction with the country that was still providing considerable amounts of materials to the USSR. That the Soviets would not move because of concerns about unrecoverable losses from an understrength division (closer to a brigade in all probability, with two regiments = attachments) and a reserve division with deficient equipment.

Regarding the Soviet ability to make a landing it is worth considering that the Soviets managed, with no WAllied support to land better than a division in the Kuril Islands, against a forces of similar strength and composition to those on Hokkaido (Kurile defenders were, on paper, close to three divisions, the 89th and 91st ID, an independent tank regiment, an air defense regiment + attachments). The initial Red Army landing was outnumbers about 5-1, but much as was the case on Hokkaido, the IJA forces were short on materials and with sub-standard training. This allowed the Soviet forces to establish a beachhead that could be reinforced, while the Japanese defenders were entirely on their own.
 
The defenses were, but were the troops still there, and were they still the elite forces that had existed? Were the aircraft still there? Was there still fuel for the aircraft there, how many of them could still fly (assuming there was fuel)?

The Seventh Division had already lost one Regiment of its best troops at Tenaru River and Edison's Ridge thanks to Colonel Ichiki's ill-advised attacks while in command of the 28th Regiment. Additional troops had been bled off for different missions (including the invasion and garrisoning of Attu), replaced by late war conscripts of much lower quality.

Moreover the 42nd was concentrated on the northwestern tip of the Island near Wakkanai in defensive positions lacking transportation some 150 miles from the Sapporo Bay region. The 7th Division was concentrated to the southeast, generally in the area of Obihiro, over 100 miles from the Sapporo area. Even today that is a difficult trek, especially if most of the troops need to move by foot. The defensive position shown near Sapporo are 32 miles apart, incapable of mutual support.

Certainly the force that are still in place (and considering the way the Japanese were bleeding troops, the difference between paper strength and actual ration strength is likely to be significant) will fight to the best of their abilities and extract a considerable toll, maybe even one that would lead an American or British planning staff to reconsider. We, however, are not talking about the WAllies, we are talking about the Red Army and Stalin, both of which were effectively numb to casualties at this point. As I have noted previously, it is probable that the Soviets would see far more value in areas like the Korean Peninsula and Manchuria which are there for the taking without causing friction with the country that was still providing considerable amounts of materials to the USSR. That the Soviets would not move because of concerns about unrecoverable losses from an understrength division (closer to a brigade in all probability, with two regiments = attachments) and a reserve division with deficient equipment.

Regarding the Soviet ability to make a landing it is worth considering that the Soviets managed, with no WAllied support to land better than a division in the Kuril Islands, against a forces of similar strength and composition to those on Hokkaido (Kurile defenders were, on paper, close to three divisions, the 89th and 91st ID, an independent tank regiment, an air defense regiment + attachments). The initial Red Army landing was outnumbers about 5-1, but much as was the case on Hokkaido, the IJA forces were short on materials and with sub-standard training. This allowed the Soviet forces to establish a beachhead that could be reinforced, while the Japanese defenders were entirely on their own.

At the beginning of the war the 7th Division consisted of three regiments, the 26th, 27th, and 28th (the 25th Regiment was sent to form the core of the Sakhalin Mixed Brigade in 1940, which later became the 88th Division in 1945). Of those three the 28th was more or less destroyed in the battles of Guadalcanal and Attu and had to be reconstituted in the homeland afterward. The other two regiments, to my knowledge, stayed in Hokkaido for the rest of the war and therefore the 7th should have retained most of its equipment and motor vehicles; the only further comment I can make is that when it was demobilized it had an unusually low roster of combat personnel for a division of this type, only 10,800. As for the 42nd, it consisted of 14,599 troops and the 101st IMB had 5,484. The subtotal for Army ground personnel on Hokkaido (excluding the IJN, which also had a significant presence there) was 101,029, with the balance being made up of a mixture of static fortress units, army artillery, construction, and supplies personnel.

As for the aircraft, they too were what was on-hand at the time of surrender and were turned over to the Americans. Giangreco states that since at least 1944 the Japanese had been taking pains to establish a strategic fuel reserve in each of the main islands (mostly on Honshu and Kyushu) to be tapped only for the final battles and deemed sufficient for carrying out the Ketsu plans, so I can only assume that there was at least enough for one-way missions on Hokkaido.

Maintenance and reliability given the deteriorating resource situation was an increasing problem for the Japanese late-war and many would-be suiciders had to turn back on their Kikusui missions at Okinawa because of engine trouble. Though the distances around the Japanese archipelago weren't nearly as great as those from Kyushu to Okinawa, that problem certainly wasn't going away. I can say, however, that in Hokkaido there were three airbases considered to be of high-quality by the US (Bihoro, Obishiro, and Chitose 1) that possessed permanent installations including dedicated maintenance and repair facilities. The complete map of Hokkaido airfields is as follows:

1535rb9.jpg

Whether or not these were sufficient to keep all 450 aircraft in flying order is probably unlikely, but it still would have been a serious threat to the Soviet fleet.

As for the Fifth Area Army's actual ability to deal with an amphibious invasion, say, at Rumoi, the immediate terrain is very mountainous, making it quite difficult for an attacker to fan out. Furthermore the region is directly linked by railways, that, if allowed to remain intact, would have permitted both the 7th Division in the east and 101st IMB in the south to send reinforcements to the area in short order to contain the opposing lodgement, basically Anzio-style. Probably the only way to ensure that their beachhead could perform a breakout would be to establish others at other points on the island, which would have had to fight their way through the strongpoints near the shore and any local reserve behind them.

I agree that a Hokkaido adventure would have been a distant priority for the Soviets, who were much more interested in carving out a sphere of influence in Northeast Asia and scooping up the natural resources of Manchuria. It's also extremely unlikely the US would have supported such a thing as well, considering the Joint Chiefs (and MacArthur) envisioned Stalin's role as strictly confined to the Asiatic mainland.
 
"Maximum Japanese resistance" is pretty much like the Decisive Darkness TL here. I think it's a bit over the top given that it's likely the Japanese will surrender at some point. But you might leave a significant resistance to be mopped up in the mountains which would amount to something like the FARC in Colombia.

Soviets would probably be spent getting Hokkaido, I don't see them adding northern Honshu to their conquests.
 
"Maximum Japanese resistance" is pretty much like the Decisive Darkness TL here. I think it's a bit over the top given that it's likely the Japanese will surrender at some point.

I should note that DD started out as an exercise in trying to create a scenario where the Soviets could plausibly invade northern Honshu. I don’t necessarily think Japan would have held out for as long as they did in the book.
 
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I should note that DD started out as an exercise in trying to create a scenario where the Soviets could plausibly invade northern Honshu. I don’t necessarily think Japan would have held out for as long as they did in the book.

Probably the only scenario in which the US would be willing to call for (and facilitate) Soviet assistance on the home islands is one in which they are defeated at Kyushu. Even that assumes they don't just give up on invasion altogether and be content with playing "the long game" of starving out the Japanese through a protracted blockade.
 
Probably the only scenario in which the US would be willing to call for (and facilitate) Soviet assistance on the home islands is one in which they are defeated at Kyushu. Even that assumes they don't just give up on invasion altogether and be content with playing "the long game" of starving out the Japanese through a protracted blockade.

I reckoned that the Americans wouldn’t have objected much to the Soviet’s occupying Hokkaido, there was a mention in Yalta of the Soviet’s going beyond the agreed boundaries if Japan continued to resist.
 
Probably the only scenario in which the US would be willing to call for (and facilitate) Soviet assistance on the home islands is one in which they are defeated at Kyushu. Even that assumes they don't just give up on invasion altogether and be content with playing "the long game" of starving out the Japanese through a protracted blockade.

I somehow picked up the impression that the original U.S. warplan for Japan was starvation and that only the threat of Soviet invasion made them consider invasion. Is that accurate?
 
I somehow picked up the impression that the original U.S. warplan for Japan was starvation and that only the threat of Soviet invasion made them consider invasion. Is that accurate?

The US interwar plan (Orange) never envisioned an invasion of the Japanese mainland, instead the hypothetical confrontation would be brought to an end through a blockade of Japan by the Navy. However, as the actual war in the Pacific progressed the Joint Chiefs agreed in 1944 that the best way to end the fighting was through a direct landing on the home islands. Seeing as how the goal was to bring about the unconditional surrender of Japan, and since no Japanese force had ever surrendered in the field, they believed that simply blockading and waiting for starvation to take effect risked the US not being able to achieve its stated aims and would lead to an unacceptable prolongation of the war.

Thus, as long as the goal was the unconditional surrender of Japan, only the Stars and Stripes flying over the Diet building could have guaranteed that goal.
 
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