What a blockade would do to Japanese merchant shipping

How effectively could Britain destroy Japanese merchant shipping?

Japanese merchant shipping would probably collapse quickly under coordinated cruiser and submarine commerce warfare.

The Japanese merchant marine would be an early and severe vulnerability. Commerce warfare can combine cruisers, submarines, distant interception, and prize crews rather than depend on one weapon or patrol zone. Removing tankers and freighters would cut the fuel, equipment, and replacement flow needed by Japanese forces overseas. That pressure would compound the fleet battle by making prolonged operations harder even where local units remained intact. Trade destruction is central to the wider blockade strategy.