Japan would retain ships to protect its own merchant fleet, and those forces could cooperate with British patrols against surface raiders. Raiders in the Indian Ocean would then face ships from both navies. Sydney's loss in November 1941 provides a counterfactual example of how that cooperation could matter. A Sendai-class cruiser accompanying Sydney could change the balance of the encounter.
Notable Point · 49:49-51:07
A Japanese cruiser alongside Sydney could change a raider encounter
Joint cruiser patrols could make a historically fatal lone-ship encounter much harder for an Axis raider.