Which British special forces would suit Operation Downfall

How useful would the SAS and SBS have been in an invasion of Japan?

Their wartime organizations and experience differed from the modern units; other commandos and Far East formations were more immediately prepared, while postwar forces later absorbed these wartime lineages.

The wartime SAS and SBS differed from the organizations familiar today. The SBS had operated mainly around Europe and the Mediterranean, while commandos and Far East formations already possessed more relevant regional preparation. Redeploying the European units would require retraining rather than simply attaching modern mission labels to them. Several wartime organizations later became the nuclei from which postwar special forces developed.