Alternate Scenario Leyte Gulf

By October 1944, Imperial Japan had less than a year left. Most historians say by then it was too late for Tokyo to avoid defeat--if it ever stood a chance. Conceivably, though, by pursuing a different approach at Leyte, the Imperial Japanese Navy (IJN) could've radically altered the course of the war. One possible alternate scenario:

• First, the Japanese don't divide the ships sailing from Brunei. All IJN vessels head for Letye via the Sibuyan sea, including those which historically entered the Surigao strait. A single IJN commander (other than Kurita) commands the entire fleet of battleships, cruisers and destroyers, including Shima's force, which joins it. The diversionary force, with its carriers, sorties from Japan as in real life, and does its utmost to attract attention. IJN submarines do not patrol near Leyte gulf but accompany the carrier force, in an attempt to ambush pursuers.
• As soon as the US subs Darter and Dace detect the IJN fleet in the Palawan passage, and radio its position and course, the Japanese increase speed to about 20 knots to make it more difficult for the subs to maneuver ahead into attack positions. In addition, they use searchlights to locate the shadowing subs. Once they're found, the Japanese ships drive them under with fire but don't send destroyers to hold them down yet. The idea is just to prevent losses such as the historical torpedoing of Kurita's flagship Atago, and other cruisers.
• Soon after diving, the US subs, although behind the IJN fleet and unable to attack, surface to resume reporting the enemy's course and speed. At first, around the morning of October 24th,  the Japanese fleet does not enter the Sibuyan Sea but continues northward a while to make it appear it intends to join the carrier force near Cape Engano (which the US fleet discovered later on October 24th).
• Soon after the IJN fleet has passed the entrance to the Sibuyan Sea, i.e. apparently has no intention of entering it, Darter and Dace radio this information--their first radio message at this point will presumably mention it. As soon as the IJN fleet hears their transmission, with its presumed message, it reverses course, relocates the US subs and holds them down with four or five destroyers from Shima's force. No longer shadowed, the IJN fleet then enters the Sibuyan sea. The US Admirals Kinkaid and Halsey are informed of the enemy's northward progress but not its advance into the Sibuyan Sea. By the evening of the 24th, when the carrier force is located they presume the whole Japanese fleet is massing near Cape Engano. Halsey moves north to intercept it, as in real life, leaving Kinkaid's weaker fleet to guard the landing force at Letye gulf.
• On its way north, Halsey's force encounters some IJN subs, and suffers a few losses. He retains more than enough strength to keep pressing north, however.
• By the morning of the 25th, the IJN fleet passes the San Bernardino Strait and advances south, past the east coast of Samar as it did historically. In this scenario, "Taffy" aircraft soon detect it and warn Kinkaid, who orders the vulnerable CVEs away while sending his battleships and cruisers north to meet the enemy. Therefore the Japanese do not see any light carriers or accompanying vessels, hence are not diverted from their southward course. The big IJN fleet heads straight for Leyte gulf. Soon it encounters Kinkaid's fleet and a massive sea battle begins.
• After spotting Kinkaid's fleet, the Japanese admiral orders an initial attack with destroyers. Their torpedoes sink or cripple several US battleships and cruisers. The IJN commander then orders his most effective warships, including Yamato and Musashi, to finish off the rest of the US fleet in a running battle eastward. A smaller force of older battleships including Fuso, Haruna and Kongo stay behind to pound the US cargo ships, supplies and troops ashore. After Kinkaid's fleet is demolished the best IJN vessels return to add their firepower to the bombardment. US forces suffer very heavy casualties on land and at sea. Many thousands of American sailors and soldiers die. Around nightfall on the 25th, the IJN fleet heads down the Surigao strait to return to Brunei.

The disaster at Leyte has grave repercussions for the US Pacific war effort. American morale and resolve plunge. After hearing of the huge casualties the US public demands an end to the war, even if it means an end to the policy of unconditional surrender, or a compromise peace. The setback tarnishes FDR, who loses the November 1944 elections. Peace follows soon afterwards, leaving Imperial Japan intact and in possession of many of its conquests including the Philippines. The invention of nuclear weapons in mid 1945 comes too late to affect the outcome.