Kriegsmarine vs IJN?
 

who would win?
assume war started 1945 between germany and japan
both navies have everything that they ever built
EDIT: germany took south africa and japan took Singapore
only consider navies, in total naval war

IJN.

Well, okay, in a surface engagement. Submarine warfare is another matter.

EDIT: Also depends a lot whether this happens under each side's land based air cover, of course.

EDIT 2: I suppose the location matters in general, regardless of air cover, too.

EDIT 3: Not to mention this is a wildly unrealistic scenario.

EDIT 4: Those sure are a lot of edits...

They were not even in the same league.

The KM was a 3d string navy. You'd need at least 1 CV to make the 2d string.

The IJN would have wiped the floor with the KM which never would have gotten within shooting range.

That would be some unbalanced logistical supply lines in that scenario.

I would agree with Tater. Germany did not have much in surface navy compared with Japan

IJN. Hands down. Even if the Germans had some kind of type advantage (only in subs), the Japanese would simply have crushed the Kriegsmarine in numbers. That's not to mention the fact that you're talking about one side with scores of CVs and another with none (unless you want to include the planned Graf Zeppelin CV).

Though this is a pretty dumb scenario, I'll go on a limb and say the Germans actually have a strategic edge here.

On the surface, the Japanese have a much superior Navy. However, even at their peak they never developed real power projection. So, though they'll basically experience next to no direct resistance when bombing (since the Kriegsmarine technically has no air arm at all, and the scenario says "only consider navies"), they can only bomb a few times before they have to run home to refuel. The practical limitations of Japan's oil supply even on its best day likely means they don't have that many runs in them.

The sum of the damage it can do to Germany is, even if not purely tactical, merely operational. Even if the IJN wipes out every German ship and sub, ultimately Germany is a land power. In a peacetime environment, it'll resupply by land. Even if the Japanese manage to mount some kind of blockade despite the distance, Germany would only be inconvenienced for a good long time.

Now, let's look at the Germans. Their surface fleet will basically be a goner, true, but it has a lot of subs. If you let them have everything they ever built, there will be something like a thousand of them, including almost 300 long range IXs and even a few XXI (and as many as over 100 if you assume all the wartime production bottlenecks that kept a lot of them from putting out to sea wouldn't appear in this peacetime-start scenario). In either case, such a force would be a critical problem even for the Allies (for all their ASW prowess and tech, the real Allies fought those thousand submarines a few score at a time as they were built and brought into action over the years), and the Japanese were relatively weak at ASW.

If you hit the Japanese merchantmen supply lines with these one thousand subs AT ONCE, or in waves of hundreds so you can maintain a continuous presence, the Japanese lines of communications would be shut down in short order, thus creating a strategic crisis in Japan. You can use some of the shorter range subs to flood the area in front of your naval bases or block off choke points and make it a truly risky business for the Japanese carrier force to come close enough to bomb.

Short version is, if you count only navies, ironically only Germany has a force structure (coupled with Japan's geography) that gives it a chance of a "strategic" win that would bring Japan to its knees and amenable to negotiations from which substantial, strategic concessions can be extracted.

Plan Z was to have:
4 CVs
6 BB
2 BC
14 CA
6 CL
6 DD

Sounds good right? But look what they would be facing!

21 CV
4 CVL
11 BB
45 CA and CL
141 DD
68 SS

If you want to talk strategically look at a map! Any German U Boats that want to attack Japanese shipping have to go though the Strait of Malacca (Guarded by Singapore) or the smaller straits in the Dutch East Indies. Otherwise they have to take the long way around and go past the Solomans!

The Japanese can just camp at the straits and take them out.

Even at Gibraltar, guarded by the British and another narrow strait, German subs managed to sneak past and into the Mediterranean. Against 1945 German subs, it is hard to believe the Japanese, with their relatively weak ASW prowess, would prevail. If a battle is forced, a likely outcome may well be the destruction of Japan's ASW ship barrier, followed by a blockade of Singapore.

The germans did not have a real navy. Period. 3d rate, if that. I'd put the KM below Italy, frankly.

No navy means zero ability to project power in the PTO. No organix air support—and KM CVs are fantasy, if you consider that, then you have to grant the IJN all their "mighta been" ships as well, any of which would WTF Pwn the KM).

Also, and this is CRITICAL—doctrine. Give the KM magical CVs in 1945, and what exactly do they do with them? What is their operational doctrine? How experienced are they in CV ops? Not at all. Heck, the IJN didn't even really absorb the lesson they taught the world—mass use of CV airpower. Singleton CVs are targets to be destroyed piecemeal.

Also, look at their planned aircraft, LOL. Navalized Ju-87s and Bf-109s. Water cooled. The first engagement, regardless of the outcome of the KM strikes would decimate their pilots since ANY damage to their liquid-cooled aircraft would result in a swim with sharks (air-cooled naval aircraft FTW).

How about escorts? LOL. How many did DDs did the KM have? 20? The USCG had more.

It's not even close. Maybe you can give Germany the UFO planes in Il-2 1946 to help them :)

BTW, the Germans never had 1000 subs at once. They serially built them to replace sunk subs—and the vast majority of the 1000+ built WERE sunk. The most they had at one time—in response to war losses—is likely higher than they would have had otherwise.

The STROG is only 50 or so miles long. The STROM is 500 miles long meaning sneaking past of not an option, the German boats would have to Snort or run on top. Also by 45 the Japanese had developed a basic MAD sensor IIRC meaning their aircraft are a major threat. Also the STROM is choked with small islands and very narrow meaning that nets and mines are a big hazard.

I'm not sure who this is targeted to, but I didn't consider KM CVs, or any part of the Z-plan for that matter. The surface fleet I'm imagining did not go further than Tirpitz, and you'll notice I didn't say anything further than they can all die.

Well, blame the scenario writer, not me. He said that despite it apparently being peacetime until that moment of war, both sides get "everything that they ever built". So those 1000 subs (the latter half of which are somehow built with the benefit of war experience despite no war having taken place) are a consequence of the scenario as given.

Besides, as I understood it, in the real war if the subs weren't sunk, they still won't have slowed down much because they were trying to increase the number of subs to put the pressure onto Britain. What might have happened is that the Type XXI might not have been built, but that's another issue.

Even a modern MAD has a sorely limited range so quite frankly I won't be placing much hope into a primitive MAD sensor.

Besides, the narrowness of the Straits works both ways in that even if the Japanese plug up the whole strait well enough the Germans can't sneak or blast past, equally the Germans have the opportunity to block off the Strait with relatively few boats and cut off the easiest route to the Suez Canal (and thus Europe). Already in this defense one major trading avenue is cut - strategically Japan is hurt, Germany not beyond the cost of sending its boats.

As for the other straits, if they are less easily accessible to the Germans, equally they'll lead to longer passages to Europe (virtual attrition). Also, the scenario gives Singapore to the Japanese, but not elsewhere, so the Japanese would find it harder to plug up most of the other straits, and the game goes rapidly downhill as the German subs starts to seep (and then break) through the gaps.

Ultimately, the problem is that between the different force structures and the geopolitical situation of the two states, Germany has the conditions to be strategically offensive, while the Japanese can only be tactically offensive and strategically defensive.

Yeah, I just reread the (weak) scenario.

Singapore of course is meaningless, the only bit of the SWPA that mattered was the NEI—OIL.

Minus oil, the KM would be just as FUBAR, frankly.

Anyway, assuming everything they built, then I suppose they get the 1000+ subs. Of course they have no possible way to replenish that many, so they are in effect spare parts. The IJN could actually supply every ship they built. Heck, they'd get the wartime merchants, too (hundreds of merchant hulls).

BTW, in addition to MAD on planes, from early on they had MAD and passive listening devices (along with controlled mines) sort of like SOSUS.

They also would have pretty good air support (excellent flying boats, etc).

Anyway, it's no contest, the 2 navies were not in the same league.

Also their existing subs that were pulled for refit or what not when they returned from patrol. Anyone know the highest number of uboats operating at sea in any point in time?? Id make a guess, but i honestly don't know this figure.

Hell, even Hitler said, something like, "on land i'm a lion, at sea i'm a coward", or words to that effect.

whats with all these rapid fire threads? first it was IJN divisions being better then a million german soldiers, then it was how you can beat a US task force, now its IJN vs KM? You should look it up. Everyone know the germans had no navy, the only acception being their underwater fleet. And the japs had LOTS of destroyers, so that wouldve taken care of that for the most part.

all of those threads have been brutally murdered, being decapitated and mangled. i personally murdered them early on. seems i was a little late on this 1.