This was a US unrealised amphibious operation to capitalise on the Japanese operational confusion occasioned by ‘Olympic’ by landing near Tokyo, the Japanese capital, on Honshu island and then taking it as the first step in the reduction of the entire island (summer 1945).
Tentatively scheduled for implementation on 1 March 1946, ‘Coronet’ was to have used a large proportion of US forces transferred to the Pacific theatre after the end of hostilities in Europe, and would have put ashore two US armies, one to each side of Tokyo on Honshu island, after the seizure of the Izu Shoto offshore island group.
Sagami Bay, to the west of Yokohama, was the landing area designated for Lieutenant General Robert L. Eichelberger’s 8th Army 1. Kujikurihama Beach to the east of Tokyo was assigned to General Courtney H. Hodges’s 1st Army 2. There were other formations available as reserve and follow-on forces including included the US Army Forces Pacific Reserve 3, and Lieutenant General C. F. Keightley’s British Commonwealth Corps (Major General L. G. Whistler’s British 3rd Division, Major General R. H. Keefler’s Canadian 6th Division and the re-formed Australian 10th Division for which no commander had yet been decided.
The overall scheme was for the armoured forces to isolate Tokyo from the rest of Japan by pushing inland onto the Kanto Plain, where Kumugaya and Kogo would be captured, while the infantry formations took Yokohama, Tokyo and the Boso peninsula.
In the face of an opposition that the US command system expected to be found by 560,000 people including 12 fully organised divisions, the Americans believed that the operation would be extremely costly in manpower terms, and were therefore extremely relieved that they did not have to implement the plan, which envisaged an inland exploitation and link-up with the forces involved in the earlier ‘Olympic’ before the four US armies swept on to crush all Japanese resistance.