Japan 45

[Outlaw Josey Wales]

I found this.  Not a lot of details, but, it's a start.

In this initial draft staff study, for the assault, First Army would command two corps, the XXIV Corps made up of the 7th, 27th and 96th Infantry Divisions, as well as the III Amphibious Corps, comprising the 1st, 4th and 6th Marine Divisions. The XXIV Corps had not been created until March 1944 but had already fought through two tough Pacific campaigns – those of Leyte and Okinawa – with all three divisions participating in both campaigns. Of the Marine Corps' six divisions, three were scheduled to take part in Operation Olympic (2nd, 3rd and 5th) while the other three were scheduled to participate in Coronet. III Amphibious Corps had landed at Guam while V Marine Amphibious Corps had landed at Saipan and Tinian in July 1944. The 1st Marine Division was the most senior formation and had fought all the way from Guadalcanal through Peleliu to Okinawa. The 4th had fought on Iwo Jima while the 6th had fought on Okinawa. Eighth Army would command three corps – X, XIII and XIV. The X Corps had been formed in the USA in May 1942 and deployed to the Pacific in July 1944 to take part in the fighting for New Guinea and fought through the campaign for Leyte. Of the three divisions, the 37th was the most experienced, having fought on New Georgia, Bougainville and Leyte. The 24th had fought on Hollandia, New Guinea and Leyte and for the remaining months of the war was engaged in clearing the southern Philippines. The 31st trained in the USA from the time it was federalised (November 1940) until it deployed to New Guinea to continue training and finally entered combat at Morotai and in April and May 1945, helped to clear Mindanao. XIV Corps would command the 6th, 32nd and 38th Infantry Divisions. The corps had been sent to the Pacific in January 1943 to command the forces on Guadalcanal once the marines had been augmented by two army divisions, and also fought on New Guinea and Bougainville. It took part in the assault at the Lingayen Gulf under Sixth Army in January 1945 and continued to take part in the Luzon campaign until August 1945. The divisions assigned to the corps were veteran divisions, the 6th was a regular army formation that entered the Pacific War at Wake Island in 1944 and participated in the Luzon campaign from the start, mostly serving under XIV Corps. The 32nd had been sent out to Australia in May 1942 and took part in the fighting for Buna from November 1942 to January 1943. It also fought in the campaign for northern New Guinea in 1944 as well as taking art in the Leyte and Luzon campaigns. The 37th, a National Guard division like the 32nd, had seen its share of fighting on New Georgia, Bougainville and the attack at Lingayen. Of the five corps slated to take part in the initial assault, the XIII, along with its two component formations, the 13th and 20th Armoured Divisions, was the only redeployed unit scheduled to take part in the opening phase. The corps had had experience of leading armoured forces across Europe, a skill lacking among the other corps headquarters as no armoured divisions were deployed in the theatre. Both armoured divisions had entered combat during the last stages of the war in Europe and suffered relatively few casualties.

On Y-Day+30, each army would receive an additional corps of three infantry divisions. When the staff study had been published, the corps headquarters had not been finalised but would have almost certainly had to have come from the forces in Europe. The six component divisions would have also had to have come from forces redeployed from Europe and were slated to include the 5th, 44th and 86th Infantry Divisions for the First Army, and the 4th, 8th and 87th Infantry Divisions for the Eighth Army. Likewise, with the exception of the 11th Airborne Division, all AFPAC reserves would be made up from redeployed units. The 97th Infantry Division, slated to be the floating reserve on Y-Day had entered combat late in the Northwest Europe campaign. The AFPAC follow-on reserve would contain three veteran infantry divisions – 2nd, 28th and 35th. The AFPAC strategic reserve would contain another three veteran divisions, the 91st which fought in Italy, as well as the 95th and 104th. While the plans failed to identify specific corps and corps commanders, Marshall made it plain to his assistant, General Hull, that he had no intention to seek MacArthur's personal approval before redeploying corps headquarters and commanders to the Pacific. Instead, he sought to select those who were acknowledged as the best from the ETO and send them out. If MacArthur had any specific objections, he could make them known at that time. Marshall suggested: III Corps under Major General James A Van Fleet; V Corps under Major General C R Huebner; VII Corps under Lt General J Lawton Collins; XIII Corps under Alvan C Gillem; and XVIII Corps under Major General M B Ridgeway (Memo, Marshall to Hull, 28 May 1945, Verifax 1193, Item 2288, Marshall Library; Message, Hull to MacArthur, 29 May 1945, Verifax 1193, Item 2799, Marshall Library). Planning documents for the naval and amphibious phases of Coronet had not been drafted when the war finished but it is evident from the AFPAC staff documentation and plans that the Navy's role in the operation and the relationship between Nimitz's staff and MacArthur's staff would have been very similar to that of Olympic. CINCPAC would plan for the naval and amphibious phases while AFPAC would plan for the land campaign. It is likely that similar arrangements would have been made for the transition of command between the naval and ground commanders as the ground forces were established ashore. Naval and air bombardment of the objective areas would start from about Y-Day-15. On Y-Day itself, the two field armies would make simultaneous landings and although the preponderance of force was with Eighth Army, in the initial staff study, neither assault was designated as a main one. First Army would land elements of the XXIV and III Amphibious Corps near the middle of Kujukuri Beach. The 7th and 27th Infantry Divisions as well as the 1st and 4th Marine Divisions would land and establish a beachhead. On Y-Day+5 the 96th Infantry and the 6th Marine Divisions would then come ashore. First Army would face three major tasks once they had come ashore. Firstly, forces would move south and west across the Boso Peninsula to tackle the defences guarding Tokyo Bay. Forces would also move northwards towards Chosi in order to secure this small port. An open corridor leads northwest towards Tokyo, bounded by Chiba and the northern shore of Tokyo Bay on its western side, as well as two lakes (Imba-Numa and Tega-Numa) to the north. First Army was to advance towards Tokyo using this corridor. Eighth Army would land on the beaches at the head of Sagami Bay with elements of X Corps and XIV Corps. The initial units to land would be the 24th and 31st Infantry Divisions (X) as well as the 6th and 32nd Infantry Divisions (XIV). After establishing a beachhead, Eighth Army would move eastwards clearing the Miura Peninsula and capture the Yokosuka Naval Base. On Y-Day+10 the XIII Armoured Corps would land and then drive straight north up the Sagami River valley, establishing blocking positions north of Tokyo from Kamagaya to Koga with XIII Corps being ready to advance towards Tokyo as necessary while other elements of Eighth Army were to capture Yokohama and assist First Army's capture of Tokyo.