February 12, 2012

What If...? #5: Opening The Locks

Admiral Osami Nagano walked into the meeting room with an ashen look on his face.  Taking his seat at the head of the table, he looked less like the Chief of the Imperial Japanese Navy's General Staff, and more like the weak leader some thought he was.  With a shaken tone to his voice, he brought the meeting to order.  "Gentlemen, I've been informed that the aircraft carrying Admiral Isoruku Yamamoto on his inspection tour of the Solomon Islands... has been shot down.  He is confirmed dead."  As the rest of the General Staff reacted to this grim news, he continued.  "Admiral Ugaki survived, but is seriously injured."  He looked around the table.  "Coming so soon on the heels of our losses.. no, let's call them what they are, our defeats, at Midway and that damnable 'Starvation Island', this is another terrible blow.  Reports are that the first of the new American aircraft carriers is nearing completion, soon to be followed by a half-dozen more.  Gentlemen, unless something is done quickly, the unstoppable tide will soon sweep over us and wash us away.  Do any of you have any plans that can balance the ledger sheet in our favor?"

Silence fell over the table.  Nagano looked at the assembled General Staff with something approaching horror on his face.  "Nothing?  Was Yamamoto the only one of us with an imagination?"  At that goading, many of the militaristic hardliners flushed angrily but remained quiet.  From the far end of the table, a quiet yet confident voice, loud in the nearly silent room, said "There is a plan we have been working on...."

When one thinks of the Imperial Japanese Navy in World War II, one undoubtedly thinks of the aircraft carriers of the Kido Butai, or the massive battleships Yamato and Musashi.  More thoughtfully, one might consider the deadly efficient force of cruisers they put to sea or their squadrons of destroyers, considered by many to be the best of the War.  Yet only rarely would any consider sparing a thought to the IJN's submarines, unless it was to react in horror to the kaiten manned torpedoes fielded as a counterpoint to the kamikaze.  This is a mistake, as the Japanese submarine force was interestingly varied, not to mention fairly successful in their generally assigned role of warship hunters.  Japanese submarines sank as many American fleet carriers (two, Yorktown and Wasp) as their conventional naval air did (Lexington and Hornet). 

On the whole, Japanese submarines were inventive and cleverly designed, if perhaps ill-used.  Without a doubt, however, there was one surprising class of submarine where they were the unquestioned best in the world.

Commander Yasuo Fujimori watched as the crew of the submarine swarmed over the undefined shape on the forward hull, rapidly attaching parts and doing other, less obvious, things.  His stopwatch ticked relentlessly as the shape rapidly gained recognizable form.  Quickly, two men climbed in and a roaring sound emanated from the object as the crew scrambled back inside the hull of the sub.  The roaring was suddenly overridden by a massive loud hissing noise, and the object was thrown down the length of the hull.  Fujimori clicked the stopwatch as the object took to the air and flew off.  Grinning, he turned to the captain of the submarine I-400.  "Seven minutes from opening the hangar to takeoff.  That seems impossible, but I just saw it with my own eyes."  The captain grunted.  "It takes longer in rough seas, but not so much that we won't be able to get all three in the air under 30 minutes.  The pilots tell me that it's all due to the engine of their plane."  He waved his hand as if to suggest he was uninterested in such things, but giving the lie to that impression, he continued.  "We preheat the engine lubricant and feed it in before engine start.  You can't do that with a radial engine like the Zero has.  No, these Seiran's are amazing beasts."  At that statement, Fujimori smiled.  "They'd better be.  Captain, let's go below.  I'd like to tell you about Operation Lockpick."

The I-400 class of submarines was entirely unknown in the west until after WWII had come to an end.  They were also the largest submarines built at 400 feet long and a displacement of around 6600 tons.  They held that honor until the 1960s, when nuclear-powered ballistic missile subs took their place.  They had an unrefueled range of over 37000 miles, and their four engines could move the massive subs at a respectable 18-1/2 knots on the surface.  Like all submarines, they carried torpedo tubes in the bow, but their primary role was that of aircraft carrier.  A pressurized, waterproof, hangar some 100 feet in length stored three M6A Seiran torpedo bombers in "collapsed" form. 

The Seiran was designed specifically for use on the I-400s.  Their wings folded hydraulically, rotating 90° both horizontally and vertically to lay against flat against the side of the fuselage.  The tail also compacted down, allowing the entire plane to fit into the 11'-0" diameter hangar.  For launch, the plane was removed from the hangar, unfolded, pre-heated oil was added to the engine, and an air-powered catapult gave the initial acceleration to get the Seiran into the air.  Floats could be added to allow recovery of the aircraft, using a collapsible crane mounted on the sail.  The plane could also be launched without the floats, allowing the carrying of a standard torpedo.

Private Christopher Hamill yawned as he leaned against the 40mm Bofors quad-mount.  Just another hot, humid day in the jungle, he thought as he watched Sgt Singleton and Corporal Lowe adjust some part of the gun.  Hamill yawned again, then began complaining.  "Sarge, why are we here?  Between you, me, and that stupid bird over there, we're about as useful as tits on a boar."  "We're defending this position," Singleton said without looking away from... whatever it was he was working on.  Hamill sighed.  "That's just my point, Sarge.  Defending it from what?  It's not like there's ever going to be an attack here."  At this pronouncement, Singleton did look up.  "Well well.  Lowe, call the MPs... looks like Yamamoto ain't dead after all, he's just gone undercover."  Hamill flushed, but gamely continued.  "C'mon, Sarge... we're an anti-aircraft battery.  The Nazis don't have any aircraft carriers, and the Japs couldn't get within 500 miles of this place and you know it."  "Hamill, shut up and get back to work.  If the Army wants us to defend the Gatun Locks, we sit here and damn well do it."

The original Japanese plan was to use eighteen I-400s to attack New York City.  After Yamamoto's death removed most of the support for the mission, the number of subs was changed to nine, then to five.  The target also changed, from New York City to the Panama Canal, then to Ulithi Atoll.  The war came to an end before any attack could be performed, however.  But if the IJN General Staff had continued to back the plans and the construction of the subs had been made a priority, there could have been a mission as early as 1944.  As written, two I-400s and two smaller aircraft-carrying submarines would surface on the Pacific side of Colombia to launch 10 Seirans.  The M6As, painted in US Army Air Forces colors, would fly across Colombia, turn west, then attack the Atlantic end of the Panama Canal with torpedoes and 850kg bombs.  The planes would then return to the subs, where the aircrews would be rescued from their ditched planes.  Interrogation of US POWs indicated that defenses around the Canal Zone had become lax, believing that there was no way they'd ever be attacked.  But the original plan was to have five of the massive CV(SS) attack.

Lieutenant Atsushi Asamura looked first to the right, then to the left of his Seiran.  The other 14 planes of Squadron Number 1 were arrayed to either side, a sight which made his heart soar.  Finally, the mission they'd trained so hard for was underway.  He took it as a good omen that all 15 planes had managed to get into the air.  He also chose to take his gunner's airsickness as a good sign; it meant that everything was going exactly as it had in training.  Maebara-san might not feel the same way though, he thought with a smile.  He frowned when he looked again and saw the American star painted on the side of the planes.  It's an insult to us to suggest we need such subterfuge to succeed in our mission, he thought.  Still, if it makes the Americans hesitate for even a few seconds, it might be enough.  They can't be on alert all the time.  The 15 planes flew on.

Using plans provided by a Japanese engineer who worked on the Canal during its construction, it was decided that while the locks on the Pacific side would be easier to damage, it was the Atlantic side that would do greater harm to the Canal if an attack was successful.  It was estimated that the Panama Canal would be out of business for six months while expected damage was repaired.  Until it was, ships transferring from the Atlantic to the Pacific would add an additional 16000 miles to their trip, not to mention having to go around Cape Horn, a location of horrible weather and the occasional iceberg.  While modern ships don't have anywhere near as many problems with the Cape as the old sailing ships did, the seas can still get high enough to make an aircraft carrier or battleship uncomfortable.  It would be even worse for smaller ships.

Captain Weymouth couldn't believe what he was seeing.  Before his eyes, the water level of Gatun Lake was dropping precipitously.  In and of itself, this was bad enough, but there were quite a few ships in sight of where he was standing, and there wasn't anything anybody could do about what would happen to them if the water level got as low it he feared it would.  Damn those Japs anyway... where the hell did they come from in the first place?  Irrationally, he slammed his hat onto the ground, then stalked towards a quad-barreled 40mm mount to chew out the gunners.  They probably didn't even see a Jap plane, he thought angrily.  They didn't even come this direction.  Things as simple as facts weren't going to let him blow off steam, though.

While destroying the Gatun Locks and preventing the use of the Panama Canal would undoubtedly be a hindrance to the American's prosecution of the War in the Pacific, in the end it wouldn't change the final outcome.  It would just add more time to the final result.  Time which would be spent further fortifying Japan, Iwo Jima, Okinawa... and further adding to the cost in lives of the final result.  In the real world, the attack was scheduled to occur in mid-1945, before it was changed to a surprise attack on the anchorage at Ulithi Atoll.  When the war ended, the I-400s surrendered peacefully, though they dumped their M6As overboard beforehand.  The aircraft carrier submarines came as quite a shock to the US Navy, which had no idea they existed.  They were studied and, eventually, scuttled.  There is only one M6A Seiran in existence.  It was recently restored and is on display at the Smithsonian Air & Space Museum in Washington.

Posted by: Wonderduck at 01:00 AM | Comments (14) | Add Comment
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Posted by: flatdarkmars at February 12, 2012 01:52 AM (I55Es)

2 If they'd pushed the issue they could have done that attack much sooner, several pre-war classes of their subs carried 1-2 planes. Other, less optimal planes were available, but even the Seiran's first flight was in '43.

As to the admittedly brief respite the blowing of Gatun Dam  would have gained them (a year at the very most) a few extra months breathing time before the B-29 raids essentially stopped domestic production could have complicated things for the allies. Historically, a whole slew of advanced fighters as well as several ships including the 16 Unryu class aircraft carriers and a gazillion fast coastal defence subs were halted or delayed when bombers got within range of the home islands, often within a few months ( or weeks) of completion or in the case of the high performance aircraft, just as production was spinning up.

A few extra months of training for the new generation of carrier pilots might have made a great deal of difference at the battle of the Philippine Sea (or whatever took its place).

A few extra months of unmolested Japanese production and aircrew training would not have changed the ultimate outcome of the war, but it could have increased the cost of ataining that outcome out of all proportion to the investment of a few subs and aircrew.

Straying rather further afield, while he canal attack would only work once,  assuming that the I-400 program retains its priority, the I-400s would be coming online in late '43 and early '44. An attack on New York and possibly Washington using disease bombs could have caused considerable mayhem. They'd have a better than even chance of succeeding as the alied ASW effort depended on radio direction finding and broken codes to track German wolfpacks, none of which would help against these boats as they'd be not be using German codebooks and wouldn't need to transmit since the knew where their target was.

Posted by: brickmuppet at February 12, 2012 02:24 PM (EJaOX)


Actually, the planners of the construction of the Panama Canal had envisioned a situation where the Gatun Locks or any of the other locks would breached (In the unlikely event of a ship managing to be so out of control that they managed to smashed through all the other safeguards.).  They built an ultimate failsafe for it - portable dams for just that eventuality, to prevent the loss of too much water.  So draining Gatun Lake was never going to happen if they simply attacked the locks.  Hitting the dam would have been more worthwhile, but the dam might have been easier to fix.  Knocking the locks out of action would still be worth it.

Of course, by 1942, the US Navy was already planning to send to sea ships larger than the canal could handle, so ultimately, it would not have meant as much either. 

As for using the I-400 - you wonder if the Japanese would have been through enough not use their radio communications at any part...



Posted by: cxt217 at February 12, 2012 04:05 PM (k9NA7)

4 @Muppet: I left the date undefined because I couldn't quite figure out the minimum construction time required for an I-400 class sub.  In my brain, the attack in the post took place in early-to-mid '44.

@cxt: I didn't know about the portable dams, and haven't seen any reference to them in my research... interesting stuff, that.  I will note that while the Navy had plans to put Panamax-plus ships to sea, ultimately they didn't in WWII.

Posted by: Wonderduck at February 12, 2012 05:43 PM (K/dx0)

5 The MONTANA class got cancelled but I believed MIDWAY herself went to sea before the end of war.  If the war had lasted any longer, MIDWAY would have been sent on the long way around to join the Pacific Fleet.

Posted by: cxt217 at February 12, 2012 06:30 PM (k9NA7)

6 USS Midway: commissioned 9/10/1945.

"...ultimately they didn't in WWII."

Posted by: Wonderduck at February 12, 2012 06:51 PM (K/dx0)


There was a nontrivial amount of shipbuilding, including warships, on the US West Coast, which wouldn't have been affected by damage to the Canal.

Quite a lot of it was intended for the European theater, but if the Canal had been taken out, they could have shuffled things around.

Also, by mid 1944 the US Navy in the Pacific was already large enough to win the war. Additional forces made that easier, but Nimitz could have won it anyway.


Posted by: Steven Den Beste at February 12, 2012 07:23 PM (+rSRq)


 The West Coast did have a lot of shipbuilding - Henry Kaiser and Marinship comes to mind - but warship construction was pretty much dominated by the East Coast yards.  The largest warships built on the West Coast during WW2 were the four OAKLAND class CLs.  Every other cruiser, battleship, light and fleet carriers, were all built on the East Coast.  So were most of the destroyers.

Nimitz and PACFLT probably had enough warships to defeat the Japanese, but the operational strain would have been immense.

I do wonder how much of MIDWAY's completion was slowed down by the imminent end of the war.  The US Navy was already cancelling ships from March 1945 on.

Posted by: cxt217 at February 12, 2012 08:30 PM (k9NA7)


There's one big shadow over the end of the war which renders most of these kinds of what-if's moot. For instance, when people talk about, "What if the Normandy Invasion had failed" or "What if the Battle of the Bulge had turned out to be a German victory", the answer to all those questions is the same: the first A-bomb would have been dropped on Berlin, and the war in Europe would have ended in early August 1945.

By the same token, these what-if's about the Pacific all have the same answer: The war ends in early August 1945 no matter what happens before that.

If, for instance, the Japanese somehow managed to preven the Americans from taking Guam and Saipan, then the B-29's carrying the bomb would have flown from western China. But they still would have flown, and the bombs still would have been dropped, and the war would still have ended.

Posted by: Steven Den Beste at February 12, 2012 08:51 PM (+rSRq)

10 Way back in my original "What If...?" post, in the beginning of 2008, you proposed (in a reaction post of your own) that the bombs would have been flown from China, Steven.  I'll repeat what I said back then here:
Not a chance.  The chance that the plane carrying the bomb would have a malfunction and crash-land someplace the Japanese could get their hands on it wouldn't be taken under ANY circumstances.  We barely let our friends know what was going on with the bomb, after all.  The flight from Tinian, on the other hand, was completely over water... perfect for jettisoning the bomb where nobody untoward could get their hands on it.

The logistical problems with flying B-29s from China are well-documented as well.  Throw in the added headaches of trying to get the various pieces of the bomb to the Chinese base, and it seems even less likely.

Posted by: Wonderduck at February 12, 2012 09:57 PM (K/dx0)


I think you underestimate the issues Truman was facing by that point. The American people were tired of war. They wanted it over with. The only alternative was the November invasion, which was estimated to be profoundly bloody and difficult.

I think Truman would have ordered them to do it anyway, irrespective of the objections you raise.

Posted by: Steven Den Beste at February 12, 2012 10:14 PM (+rSRq)

12 You forget the third alternative, blockade.  Much less costly than invasion, at least for the US, and they'd be able to discharge a rather large amount of men to boot.  The Navy backed the plan, and it's pretty clear it would have worked very well by that time.  Japan would have starved to death, but that would have been a minor consideration by then.

I don't doubt that the bombs would have been dropped; just not from China. 

Posted by: Wonderduck at February 12, 2012 11:37 PM (K/dx0)

13 When I suggest the war might have continued longer or been more costly, it only would have been so until bases in B-29 range could be secured. If the IJN and IJA had upgraded their air forces in the interim then there would have been a reduction operation until their air forces had been culled sufficiently to allow the atomic bombs to be delivered.

Unlikely that the war lasts past early to mid '46.  Even if something like Hatanaka's gambit had succeeded, we would see operation Downfall, which in its post trinity version involved the use of 14 nukes. I can't see it going on past mid '46.

Note too that if the war goes much past August '45 AT ALL, then MILLIONS of Japanese start starving. One of the things the Allies discovered when they landed was that Japan was essentially out of food, the US and Commonwealth navies spent the winter shipping food in.

I agree with Wonderduck that nukes from China is a non starter. The nationalists were actually backed and trained by the U.S.S.R. and the other force in China was the Maoists. We were NOT going to send our super secret weapon there to be handed over to Stalin (we had our own academics to take care of that).

Posted by: brickmuppet at February 13, 2012 12:34 AM (EJaOX)


American war-wariness was a major concern for Truman and officials within his administration - which is incidentally one of, though not the only, reasons for unconditional surrender - but nothing I have read about and from Harry Truman supports the proposition that he would launch the nuclear-equipped B-29s from China or any place where the bomb would not have absolute security because of domestic considerations.  FDR might have considered it (Though even he was not likely to approve it.), but not Truman.  There was a better chance of the USAAF perfecting in-flight refueling to allow a longer-range B-29 flight than a China base scenario.

That the Japanese was running out of food would have shorten the war, but since the Japanese military and government had made it clear they would let millions of Japanese civilians starve to insure the military remained fed, I doubt it would have shortened the war too much.  Lack of materials to fight the war would have done much more to shorten to war, but not that much sooner, even with a full scale blockade being launched.

One thing which becomes clear is that Japan was really fortunate they surrendered when they did.  Even a delay of a few more months would have seen XXI Bomber Command focus B-29 attacks on the Japanese rail system while maintaining their mining operations.  If the former had happened, it would have crippled the Japanese rail system, which meant millions of Japanese would have starved even AFTER surrender because the distribution system had been wrecked.

This is the irony when people base their arguments against the use of the atomic bomb on the USSBS, which assumed the USAAF kept pounding Japan with B-29 raids.  Dying of starvation is no less pleasant than dying from nuclear attack.

Posted by: cxt217 at February 13, 2012 05:27 PM (k9NA7)

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