Conkristador's KANTAI KESSEN
Posted: Mon Sep 07, 2026 3:27 pm
An alternate history for War in the Pacific: Admiral's Edition — scenario 105
It is not a list of unit tweaks. It asks one question and follows it everywhere it goes: what does the Pacific War look like if the naval treaties never happened?
DOWNLOAD: CRS KANTAI KESSEN The premise — six changes
The trade at the centre of it
Twenty years of unrestricted naval building has to be paid for, and it is paid for out of both armies.
Japan completed the 8-8 Fleet exactly as the Diet authorised it in 1920 — eight battleships and eight battlecruisers, sixteen capital ships on the first morning. The Navy won the budget war outright, so the Imperial Army is thinner than it was, its 1944 and 1945 raisings are months late, and Japanese heavy industry is 21% smaller because the money went into hulls. America built the 1916 Program and kept building, which is exactly why the draft lapsed in 1941.
Both navies are enormous. Both armies are starved.
The carrier war is smaller as a direct consequence. Akagi, Kaga, Lexington and Saratoga were carriers only because Washington saved their hulls from the scrapyard; here they complete as the capital ships they were laid down as, and both sides replace them with smaller purpose-built decks. Deck counts roughly hold. Aircraft numbers do not.
What you get instead is a plausible alternate history focused on big guns. Sixteen Japanese capital ships against an American line reinforced by four battlecruisers. Night action, the Long Lance and crew ratings decide things that carriers decided before.
The road to war
What is different when you actually play it
There is no Pearl Harbor raid
Kido Butai deploys to the interception line instead. Japan does not need to forestall the American fleet — it needs the American fleet to come west, into a Mandate barrier that has been fortifying since 1919. Guam is a fortress inside that barrier; Truk and Saipan are fortified in reply. The Central Pacific is a wall in both directions.
The first morning is spent taking Indochina
Cam Ranh Bay falls in the night with the two captured French capital ships in it — and the garrison fired the fuel farm, blew the cranes and scuttled in the fairway on the way out, so Japan owns a wrecked anchorage and 12,000 tons of supply where there were 73,000. Saigon and Haiphong are still being fought for at turn one, against the Cochinchina brigade, the 9e RIC, the 5e REI and the colonial gunners. The Imperial Guards Division and two tank regiments are coming up the road from Battambang.
Because Saigon is hostile, the Genzan, Kanoya and Bihoro rikko are at Hainan and on the Thai fields instead — and they sank Force Z from Saigon at four hundred miles. Force Z's fate is a real question in this scenario rather than a scripted one. The Borneo invasion convoys stage from Takao and cannot start until Cam Ranh is working.
The gun war is the main event
Sixteen Japanese capital ships, including the four Kongos and Akagi, Kii, Owari and Suruga as 41,200-ton battlecruisers, against an American line reinforced by four battlecruisers of its own. Yamato joins in May 1942. The two Number 13 hulls — 47,500 tons and 18.1in guns — were starved on the slip and complete in 1944, eight years late and long after they could have decided anything.
Japan's night-fighting advantage is real but smaller than it was: extreme night torpedo work was the answer to being outnumbered five to three, and a fleet that can fight in daylight did not train to that pitch in the dark. The gap is twenty-seven points, not forty-three.
The ships the treaties actually distorted
London 1930 capped destroyers at 1,500 tons, with only 16% of tonnage allowed up to 1,850. Japan tried to put Fubuki armament on a 1,400-ton hull anyway and got Tomozuru capsizing in March 1934 and the Fourth Fleet typhoon buckling hulls in September 1935; Hatsuharu and Shiratsuyu were rebuilt with their guns cut. Here neither compromise happens and both classes are Asashio-sized with the full battery.
The American half is more literal. The US spent its entire over-1,500-ton allowance on thirteen ships — the Porters and the Somers, 1,850 tons and eight 5in — and put everything else into 1,365-ton Farraguts. Without the clause there are more leaders, and every Farragut and Mahan is two to three hundred tons heavier.
The US Army is late, and Japan can escort a convoy
The draft lapsed, so 1942 American formations are six months late and 1943 formations four, and the autumn reinforcement of the Philippines never sailed. America has ships and aircraft and very few soldiers until 1943. The Marine Corps is untouched.
On the other side, the 1937 reorganisation gives Japan a Sea Escort Command running from January 1942, kaibokan a year early, and tankers and repair ships it historically did without. The 1943 convoy massacre is not a foregone conclusion. Note that Japanese escorts will not appear on the DE line of the reinforcement screen — that is stock AE behaviour, not a bug: the game's DE filter is class type 13, which is Allied-only, and Japanese kaibokan are type 15.
Download and install
Bug reports, balance feedback and arguments about the history are all welcome. Especially the arguments about the history.
Kantai Kessen is a full alternate-history scenario built on Conkristador's Realism Scenario 1.1. It runs 7 December 1941 to 31 March 1946 on the standard map, and it is self-contained — you do not need CRS installed, and no map, art or pwhexe.dat file is touched. It adds files numbered 105 and nothing else.Two navies spent twenty years planning one battle. This is the war in which they get to fight it.
It is not a list of unit tweaks. It asks one question and follows it everywhere it goes: what does the Pacific War look like if the naval treaties never happened?
DOWNLOAD: CRS KANTAI KESSEN The premise — six changes
- Versailles, 1919. Japan is given German New Guinea outright rather than as a C-class mandate. Rabaul has been a Japanese naval base for twenty-two years, and it is fortified.
- Washington, 1922. The conference collapses, and the London treaties of 1930 and 1936 never follow it. Nineteen years of unrestricted building by everybody.
- Tokyo, 1937. The high command reorganisation works. Japan gets escorts, tankers and a real pilot training programme.
- Saigon, 1940. Governor-General Catroux refuses the Vichy recall and takes Indochina over to de Gaulle. Japan's southern springboard is hostile ground.
- Washington, August 1941. The Selective Service extension fails by the one vote it historically survived by.
- Berlin, 11 December 1941. Hitler says nothing at all.
The trade at the centre of it
Twenty years of unrestricted naval building has to be paid for, and it is paid for out of both armies.
Japan completed the 8-8 Fleet exactly as the Diet authorised it in 1920 — eight battleships and eight battlecruisers, sixteen capital ships on the first morning. The Navy won the budget war outright, so the Imperial Army is thinner than it was, its 1944 and 1945 raisings are months late, and Japanese heavy industry is 21% smaller because the money went into hulls. America built the 1916 Program and kept building, which is exactly why the draft lapsed in 1941.
Both navies are enormous. Both armies are starved.
The carrier war is smaller as a direct consequence. Akagi, Kaga, Lexington and Saratoga were carriers only because Washington saved their hulls from the scrapyard; here they complete as the capital ships they were laid down as, and both sides replace them with smaller purpose-built decks. Deck counts roughly hold. Aircraft numbers do not.
What you get instead is a plausible alternate history focused on big guns. Sixteen Japanese capital ships against an American line reinforced by four battlecruisers. Night action, the Long Lance and crew ratings decide things that carriers decided before.
The road to war
What is different when you actually play it
There is no Pearl Harbor raid
Kido Butai deploys to the interception line instead. Japan does not need to forestall the American fleet — it needs the American fleet to come west, into a Mandate barrier that has been fortifying since 1919. Guam is a fortress inside that barrier; Truk and Saipan are fortified in reply. The Central Pacific is a wall in both directions.
The first morning is spent taking Indochina
Cam Ranh Bay falls in the night with the two captured French capital ships in it — and the garrison fired the fuel farm, blew the cranes and scuttled in the fairway on the way out, so Japan owns a wrecked anchorage and 12,000 tons of supply where there were 73,000. Saigon and Haiphong are still being fought for at turn one, against the Cochinchina brigade, the 9e RIC, the 5e REI and the colonial gunners. The Imperial Guards Division and two tank regiments are coming up the road from Battambang.
Because Saigon is hostile, the Genzan, Kanoya and Bihoro rikko are at Hainan and on the Thai fields instead — and they sank Force Z from Saigon at four hundred miles. Force Z's fate is a real question in this scenario rather than a scripted one. The Borneo invasion convoys stage from Takao and cannot start until Cam Ranh is working.
The gun war is the main event
Sixteen Japanese capital ships, including the four Kongos and Akagi, Kii, Owari and Suruga as 41,200-ton battlecruisers, against an American line reinforced by four battlecruisers of its own. Yamato joins in May 1942. The two Number 13 hulls — 47,500 tons and 18.1in guns — were starved on the slip and complete in 1944, eight years late and long after they could have decided anything.
Japan's night-fighting advantage is real but smaller than it was: extreme night torpedo work was the answer to being outnumbered five to three, and a fleet that can fight in daylight did not train to that pitch in the dark. The gap is twenty-seven points, not forty-three.
The ships the treaties actually distorted
London 1930 capped destroyers at 1,500 tons, with only 16% of tonnage allowed up to 1,850. Japan tried to put Fubuki armament on a 1,400-ton hull anyway and got Tomozuru capsizing in March 1934 and the Fourth Fleet typhoon buckling hulls in September 1935; Hatsuharu and Shiratsuyu were rebuilt with their guns cut. Here neither compromise happens and both classes are Asashio-sized with the full battery.
The American half is more literal. The US spent its entire over-1,500-ton allowance on thirteen ships — the Porters and the Somers, 1,850 tons and eight 5in — and put everything else into 1,365-ton Farraguts. Without the clause there are more leaders, and every Farragut and Mahan is two to three hundred tons heavier.
The US Army is late, and Japan can escort a convoy
The draft lapsed, so 1942 American formations are six months late and 1943 formations four, and the autumn reinforcement of the Philippines never sailed. America has ships and aircraft and very few soldiers until 1943. The Marine Corps is untouched.
On the other side, the 1937 reorganisation gives Japan a Sea Escort Command running from January 1942, kaibokan a year early, and tankers and repair ships it historically did without. The 1943 convoy massacre is not a foregone conclusion. Note that Japanese escorts will not appear on the DE line of the reinforcement screen — that is stock AE behaviour, not a bug: the game's DE filter is class type 13, which is Allied-only, and Japanese kaibokan are type 15.
Download and install
- Requires War in the Pacific: Admiral's Edition at a recent official patch level. Built and tested against 1128.
- Self-contained. You do not need CRS 1.1. No map, art or pwhexe.dat file is modified. Only files numbered 105 are added.
- Copy everything in the archive's SCEN folder into your game's SCEN folder. Kantai Kessen appears as scenario 105.
- Start a new game. A save carries the scenario data it was created with.
- If you already use slot 105, back those files up first. To uninstall, delete the files numbered 105.
Bug reports, balance feedback and arguments about the history are all welcome. Especially the arguments about the history.