British warships were already examining Japanese merchant traffic in the region before the specific warning about Asama Maru. Intercepting the flagship of Japan's merchant fleet close to the home islands demonstrated that the Royal Navy could threaten Japanese trade while Japan could not answer symmetrically near Britain. In this interpretation, the operation combined economic warfare with deterrent signalling, and the United States was another audience. A visible British ability to operate in the Pacific could strengthen American interest in Britain's survival in the Atlantic war.
Chapter · 53:58-57:34
A deterrent demonstration near Japan
Stopping the prestige liner advertised British reach to Japan and continued Royal Navy relevance to the United States.