a pattern of American commerce on the river began to emerge. On 17 January 1918, armed Chinese men attacked Monocacy and she was forced to return fire with her 6-pounder gun. Passenger and cargo service by American-flag ships began in 1920 with the Robert Dollar Line and the American West China Company. They were followed in 1923 by the Yangtze River Steamship Company, which stayed on the river until 1935, long after the other American passenger-cargo ships were gone. 1920–1930 In the early 1920s, the patrol found itself fighting the forces of warlords and bandits. To accommodate its increased responsibilities on the river, the United States Navy constructed six new gunboats in Shanghai during 1926–1927 and commissioned them in late 1927–1928 during the command of Rear Admiral Yates Stirling, Jr. to replace four craft, originally seized from Spain during the Spanish–American War, that had been patrolling since 1903. All were capable of reaching Chungking at high water, and all year-round. Collectively referred to by the U.S. press as "the new six", and were the largest, and next in size, and and the smallest. These vessels gave the Navy the capability it needed at a time when operational requirements were growing rapidly. In the late 1920s, Chiang Kai-shek and the Northern Expedition created a volatile military situation for the patrol along the Yangtze. 1930–1942 After the Japanese took control of much of the middle and lower Yangtze in the 1930s, American river gunboats entered into a period of inactivity and impotence. During the early-1930s, National Revolutionary Army took control of much of the north bank of the middle river. The climax of hostilities occurred in 1937 with the Rape of Nanking and the sinking of Panay by the Japanese. The USS Panay incident was the first loss of a U.S. Navy vessel in the conflict which would soon become World War II. Just prior to the Attack on Pearl Harbor, most of the ships on the Yangtze River Patrol were brought out of China, with only the smallest gunboats, Wake (the renamed Guam) and Tutuila remaining behind. Wake, at Shanghai, was subsequently captured by the Japanese. Tutuila, at Chungking, was turned over to the Chinese. When the other gunboats reached Manila, the Yangtze River Patrol was formally dissolved when, on 5 December 1941, Rear Admiral Glassford sent the message, "COMYANGPAT DISSOLVED". Subsequently, the evacuated ships were all scuttled, or captured with