In 2014 China commissioned a new and exceptionally large (4,000 ton) patrol ship for its Coast Guard. That was just the beginning an even larger, 12,000 ton, patrol ship (CCG 3901) is nearing completion. While neither of these huge patrol vessels carriers much in the way of weapons both have surface and air search radars, a helicopter, boarding craft and space for several hundred people. These could be victims of some maritime disaster, or troops for some emergency in the South China Sea (like reinforcing the garrison of an artificial island). The 12,000 ton patrol ship apparently will have a 76mm gun, two smaller (30mm or so) autocannon and two heavy machine-guns.
The 4,000 ton large patrol ships have top speed of 36 kilometers an hour and supplies (food, fuel) to stay at sea for at least three weeks at a time. These ships have a desalination system to supply their own water at sea and an all-electric drive and a propulsion system designed to give the ship high maneuverability and the ability to maintain position in rough weather.
China is building several dozen of these larger patrol ships, ranging size from 1,500 tons to 12,000 tons. All appear to be in support of the Chinese assertion that their “coastal waters” extend more than a thousand kilometers from the Chinese mainland. The large coast guard ships can stay at sea for a long time and also deliver supplies to small island garrisons.
China is not the only nation to build large coast guard ships. Japan has some 6,500 ton patrol vessels. The first of these entered service in 1992 and was built specifically to escort cargo ships carrying plutonium. This was best done if both cargo ship and armed escort did not have to refuel. This ship, the Shikishima, was a coast guard ship and had light armament (a twin 35mm autocannon and two 20mm autocannon plus machine-guns). Also carried were two helicopters. It was also noted that Shikishima was ideal for service off Somalia with the anti-piracy patrol and for rushing to help during natural disasters in East Asia. By 2010 it was decided to build another Shikishima and that one entered service in 2013. By then China was already building many more of these large supply ships. These were not for escort, security and disaster relief but for maintaining China’s aggressive claims to the South China Sea.