One significant event which Cockchafer was involved in was the Wanhsien Incident in August and September 1926. Wanhsien, now known as Wanzhou District, is a port on the Yangtze River about 1,500 miles (2,400 km) upstream from Shanghai. The local warlord, Marshal Wu Pei Fu controlled the area and his local commander was General Yang Sen.
Following friction earlier in the year, General Yang's troops seized the British merchant ship, SS Wanhsien in August 1926,[5] which belonged to The China Navigation Company[6] of the Swire Group. The crew of Cockchafer heard the British crew calling for help and sent an officer and boarding party to Wanhsien to investigate. They found the ship occupied by 100 Chinese soldiers. The Navy party obtained the release of the ship after a heated argument.
On 29 August 1926,[7] China Navigation Co. ship, SS Wanliu[6] suddenly made a U-turn while a wooden boat full of Chinese soldiers, guns, bullets and allowances passed by. The wave caused by the movement of Wanliu capsized the wooden boat. 58 soldiers were drowned.
Thousands of bullets, hundreds of guns and some allowances were lost. Wanliu steamed upstream while the Chinese soldiers aboard attempted to capture the ship. They were unable to do so by the time Wanliu reached Wanhsien where Cockchafer sent a boarding party to remove the soldiers.
The reports about the escape of Wanliu reached General Yang whose troops captured SS Wanhsien again. The British officers were held aboard.[5] Another British merchant ship SS Wantung was also captured. Chinese troops with artillery gathered on the shore. General Yang seized several of Cockchafer's Chinese crewmembers who were ashore and one was killed in full view of the rest of the crew. Yang refused to negotiate with the commander of Cockchafer and the senior officer on the Upper Yangtze, commander of Widgeon headed for Wanhsien while Cockchafer remained with Wanhsien in a standoff with the overwhelming numbers of Chinese troops.
On 1 September 1926 Widgeon arrived at Wanhsien but negotiations did not go well and the rear admiral on the Yangtze decided that the matter would have to be settled by force. A British merchant ship, SS Kiawo, was camouflaged and armoured and manned by a naval crew gathered from Cockchafer, the light cruiser Despatch, Scarab and Mantis boarded Kiawo and she sailed on 4 September 1926.[5]
In the evening of 5 September 1926 Kiawo arrived in sight of Wanhsien. The plan was to board and re-take SS Wanhsien and SS Wantung while Widgeon and Cockchafer provided covering fire. Kiawo came under fire from the Chinese troops ashore. She came alongside Wanhsien and boarded under fire. The boarding party rescued the British seaman held on board after fierce fighting.
In the meantime, Chinese troops onshore and aboard Wantung opened fire on Cockchafer and Widgeon which returned fire. The boarding party aboard SS Wanhsien suffered a number of casualties including the senior British officer from Despatch and Cockchafer's sub-lieutenant who were killed. Having rescued the British merchant seamen on board SS Wanhsien, the attacking force retired to SS Kiawo. After an hour of fighting, the action was discontinued and the two merchant ships were abandoned. The British ships then retired having rescued the crews, but having lost the ships.
The British ships caused casualties of nearly a thousand Chinese civilians and soldiers in the Wanhsien Incident. Thousands of shops and homes were destroyed by shells. In the end, General Yang was pressured to release SS Wanhsien and SS Wantung. It is unclear whether the British paid any compensation.