バラバク海峡
Chester commanded the first Z Special Unit operation in Borneo during World War II: Operation Python I. This operation took place in early October 1943, and reported on Japanese sea-traffic in the Sibutu Passage and the Balabac Strait of the Sulu Sea, just to the north of North Borneo. The unit landed on Labian Point in North Borneo, opposite the Tawi-Tawi islands. Chester also provided support for a band of Filipino guerrillas under the command of an American officer, Captain J. A. Hamner. Chester was in touch with the East Coast of North Borneo: "He made many visits to his friends ashore there. He maintained communication with them by means of submarine and radio, and helped form guerrilla bands on the east coast. His visits were not always secret and he often moved rapidly from place to place with the Japanese and a pack of spies in close pursuit." He heard of the plans for an uprising against the Japanese and advised that it be postponed until the Allied forces were in a position to advance into Borneo; his advice was not heeded and the Double Tenth rebellion of the night of 9/10 October 1943 in North Borneo under the leadership of Albert Kwok resulted in the deaths of many Japanese. Thousands more local people died in the reprisals that followed.