In January 1939 Japanese authorities detained a British merchant ship at Tsingtao over alleged aid to China. HMS Birmingham entered the harbor, put a small boarding party aboard the detained vessel, and announced that it would leave the next morning. Three Japanese heavy cruisers trained their guns on Birmingham, which answered by aiming at their bridges. The Japanese ships backed down. The pressure came from the wider cruiser force, since Birmingham's unlocated colleagues could attack Japanese trade elsewhere.
Notable Point · 35:53-37:59
HMS Birmingham's Tsingtao showdown
A single light cruiser recovered a detained merchant ship because Japan had to consider what the rest of the British cruiser force might do.