River gunboat

The fictional USS San Pablo described in Richard McKenna's The Sand Pebbles is an example of this class of vessel, serving on the US Navy's Yangtze Patrol.

Various European powers, the USA, and Japan, maintained flotillas of these shallow draft gunboats patrolling Chinese rivers.

The advantages of steam power and shallow drafts meant that the new European vessels initially vastly outclassed anything available to the Chinese.

Royal Navy (RN) gunboats, numbering on average 15 a year in Chinese waters, served as "station ships", assigned to specific ports, and were designed for river functions.

The purpose built river vessels of the Insect and Fly classes which had seen service in the Mesopotamian Campaign in the Middle East and on the Danube during the First World War were deployed to China during the interbellum and took part in events of the period of the Japanese invasion of China and the beginning of the Pacific theatre of the Second World War.

In 1914 two 204-ton, 50-man patrol craft of British design and built at Mare Island Naval Shipyard were disassembled, shipped to China, and reassembled in Shanghai.