The Yangtze Patrol, also known as the Yangtze River Patrol Force and Yangtze River Patrol or YangPat and ComYangPat, from 1854–1949, was a prolonged naval operation to protect American interests in the Yangtze River's treaty ports. The Yangtze Patrol also, patrolled the coastal waters of China, protecting U.S. citizens, their property, and Christian missionaries.
The Yangtze River is the longest river in China, and has always been important to the commerce of the country. Ocean-going vessels were able to proceed as far upstream as the city of Wuhan. This squadron-sized unit cruised the waters of the Yangtze from Shanghai on the Pacific Ocean into the far interior of China at Chungking. 
In 1868, patrol duties were carried out by the Asiatic Squadron of the U.S. Navy.
In 1902, the United States Asiatic Fleet took control of the operations of the Yangtze Patrol.
In 1922, the "YangPat", an abbreviated shortening of Yangtze Patrol, was established as a formal component of the U.S. Navy in China.
In 1942, at the beginning of World War II, the Yangtze Patrol effectively ceased operations in China because of the limited resources of the U.S. Navy which needed the patrol crews and their ships elsewhere in fighting the Japanese forces in Asia and the Pacific.
Following the end of World War II, the Yangtze Patrol resumed their duties in 1945, but on a smaller and limited basis with less ships on the Yangtze River during the Chinese Civil War. When the Chinese Communist forces eventually occupied the Yangtze River valley in 1949, the U.S. Navy permanently ceased operations and disbanded the Yangtze Patrol.
As a result of the "unequal treaties" imposed on China by Great Britain and other European powers after the First Opium War (1839–1842) and Second Opium War (1856–1860), China was opened to foreign trade at a number of locations known as "treaty ports" where foreigners were permitted to live and conduct business. Also, created by the treaties was the doctrine of extraterritoriality, a system whereby citizens of foreign countries living in China were subject to the laws of their home country, not those of China. Most favored nation treatment under the treaties assured other countries of the privileges afforded Great Britain, and soon many nations, including the United States, operated merchant ships and navy gunboats on the waterways of China.
During the 1860s and 1870s, American merchant ships were prominent on the lower Yangtze River, operating up to the deepwater port of Hankow 680 mi (1,090 km) inland. The added mission of anti-piracy patrols required U.S. naval and marine landing parties be put ashore several times to protect American interests. In 1874, the U.S. gunboat, USS Ashuelot, reached as far as Ichang, at the foot of the Yangtze gorges, 975 miles (1,569 km) from the sea. During this period, most US personnel found a tour in the Yangtze to be uneventful, as a major American shipping company had sold its interests to a Chinese firm, leaving the patrol with little to protect. However, as the stability of China began to deteriorate after 1890, the U.S. naval presence began to increase along the Yangtze.
In 1901, American-flagged merchant vessels returned to the Yangtze when Standard Oil Company placed a steam tanker in service on the lower river. Within the decade, several small motorships began hauling kerosene, the principal petroleum product used in China for that company. At the same time, the Navy acquired four Spanish vessels (the gunboats USS Elcano, Quiros, Villalobos and Callao), which it had seized in the Philippines during the Spanish–American War. These vessels became the core of the Yangtze River patrol for the first dozen years of the 20th century, but they lacked the power to go beyond Ichang onto the more difficult stretches of the river.
The USS Palos and Monocacy were the first American gunboats built specifically for service on the Yangtze river. The Mare Island Naval Shipyard in Vallejo, California built them in 1913. The U.S. Navy then had them disassembled and shipped to China aboard the American steamer Mongolia. The Kiangnan Shipyard in Shanghai reassembled them and put them into service in 1914.
Later in 1914, both vessels demonstrated their ability to handle the rapids of the upper river when they reached Chungking, which was more than 1,300 mi (2,100 km) from the sea, and then went further to Kiating on the Min River. In 1917, the U.S. entered World War I. The U.S. rendered the guns of Palos and Monocacy inoperable to protect Chinese neutrality. After China entered the war on the side of the allies, the U.S. Navy reactivated the guns.
In 1917, the first Standard Oil tanker reached Chungking, and a pattern of American commerce on the river began to emerge. On January 17, 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.
In the early 1920s, the patrol found itself fighting the forces of deadly warlords and ruthless bandits. To accommodate its increased responsibilities on the river, the Navy constructed six new gunboats in Shanghai during 1926–1927 and commissioned 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 two year-round. Collectively referred to by the U.S. press as "the new six", USS Luzon and Mindanao were the largest, USS Oahu and Panay next in size, and USS Guam and Tutuila the smallest. These vessels gave the navy the capability it needed at a time when operational requirements were growing rapidly.
After the Japanese took control of much of the middle and lower Yangtze, in 1930s, American river gunboats entered into a period of frustrating 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 US 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 their crews and imprisoned by the Japanese, after the fall of Corregidor in mid-1942. Luzon was later salvaged and used by the Japanese. USS Asheville (PG-21) was sunk in battle 3 March 1942 and Mindanao was scuttled on 2 May; the USS Oahu (PR-6) was sunk in battle 5 May 1942.
After the surrender of Japan, some patrols on the river were resumed in September 1945. A few days after Japan's surrender, Adm. Thomas C. Kinkaid commander of the 7th Fleet, sailed south aboard the USS Rocky Mount to rendezvous with TASK Force-73 and continue on to the city of Shanghai, China. However, they were delayed due to the river being swept for mines and a large typhoon. They finally proceeded up river and arrived in Shanghai on 19 September 1945, with the first allied ships in over 3 years. The American flotilla made a very strong naval presence, with the command ship (USS Rocky Mount), 2 Light cruisers, 4 destroyers, 12 destroyer escorts, many PT boats and mine sweepers - a force that included the destroyer USS Eaton and light cruisers USS St. Louis and USS Nashville (CL-43) - along with a British Naval contingent of 3 light cruisers, 6 destroyers, 6 destroyer escorts and some mine sweepers, USS Nashville was relieved in November by the brand new heavy cruiser USS St. Paul (CA-73).
When the Chinese Civil War finally reached the Yangtze Valley, in 1949, the U.S. Navy permanently ceased operations on the Yangtze River and officially disbanded the Yangtze Patrol.
USS Yantic (IX-32) (1874)
USS Elcano (PG-38) (1902-1928)
USS Villalobos (PG-42) (1903-1928)
USS Monocacy (PG-20) (1914-1939)
USS Penguin (AM-33) (1923-1941)
USS Asheville (PG-21) (1926-1927)
USS Luzon (PG-47) (1927-1942)
USS Tutuila (PR-4) (1928-1937)
USS Mindanao (PR-8) (1928-1941)
USS Tulsa (PG-22) (1929-1941)
USS Oahu (PR-6)
USS Eaton (DD-510) (1945)
USS St. Louis (CL-49) (1945)
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