The Royal Navy's expanding weight in the Indian Ocean

Which navy was largest in the Indian Ocean campaign?

The Royal Navy, especially after Operation C and the release of major units following Italy's surrender.

The Royal Navy was the largest naval presence in the Indian Ocean for most of the campaign, especially after Operation C. That scale did not always produce a decisive battle because ships were dispersed across escort, deterrence, amphibious, and support missions. Italy's surrender released heavier units from Mediterranean commitments and accelerated the eastward buildup. Much of the force later known as the British Pacific Fleet first assembled, trained, and sustained itself through the Indian Ocean, making the theater a foundation for renewed British operations against Japan.