Perhaps as an effort to persuade North Korea to drop its nuclear weapons program China recently allowed public discussion of the current size of its “civilian reserve fleet” that would be mobilized quickly for a major amphibious operation. This fleet is huge in large part because since 2000 China has offered subsidies to shipping companies to make a few modifications to ferries and other RO/RO ships and agree to make them available to the military for short periods of amphibious training and extended use during wartime. For decades before 2000 China had used a system where it kept track of hundreds of commercial ferries and barges that could be mobilized by the military and used for amphibious operations against Taiwan or, it is now implied, North Korea. It is believed that there is now sufficient lift for about a dozen divisions plus non-specialized ships (mostly civilian) for moving support units.
In the West this practice goes back centuries and came to be known as STUFT (Ships Taken Up From Trade) and the current size of that Chinese fleet of recently built (with modifications for military use) ships could quickly assemble and move over 100,000 troops and 20,000 or more vehicles (combat and support) in one trip. The distance from the north China port (and fleet base) of Dailan and landing areas along the North Korean west coast is about 300 kilometers, not much farther than the 180 kilometers distance from China to Taiwan.
In early 2015 China was seen using a 20,000 ton civilian RO/RO (Roll On/Roll Off) ferry for transporting troops and vehicles during an amphibious training exercise. Many more RO/RO ships of that size have been built and entered service to date. About fifteen could be concentrated at Dailan, in addition a dozen ocean going ferries built to carry 1,400 passengers and over 200 vehicles. Meanwhile there is the growing number of amphibious ships serving full time in the navy.
Starting in the 21st century China also began building a lot more amphibious ships. This was largely an effort to replace aging Cold War era relics while upgrading the amphibious fleet overall. Currently China has four LPDs (the U.S. has nine), nearly a hundred landing ships (LSMs and LSTs) and nearly 200 landing craft. The LPDs and landing ships can cross oceans while the landing craft can reach Taiwan and are mainly coastal but are often carried by larger ships for long distance voyages.
The Chinese LSTs (landing ship, tank) can carry 2,000 tons. The Type 067 LCU can carry 50 tons for up to 800 kilometers and remain at sea for ten days at a time. These seagoing LCUs can operate in rough water while using its own navigation system. These Type 067s have been around for a long time. The first version began building in the 1960s and 130 were put into service. A scaled up version of the Type 067, the Type 271, can carry the latest, heavier (50 ton) Chinese tanks.
Most of the smaller amphibious craft actually belong to the army and, until recently you could tell that because the army ships were painted blue, while the navy ones were gray. But now the army is also painting its ships gray so you will have to get a closer look to tell who owns what. That is even more difficult now that the army is building more large ships, like new one the army officially describes as a RO/RO (Roll On/Roll Off) ship but on closer examination it is an LSM that can carry a dozen vehicles and about two hundred troops. In other words a mechanized infantry company. The new LSM was built in an army shipyard, has ramps in front and back and is armed with four 14.5mm machine-guns.
Since 2000 more landing craft have been built that can operate far at sea. This shows that the Chinese had their eyes on the South China Sea for some time and built all these long-range amphibious ships in anticipation of going after small islands and reefs far from the coast. But in the meantime this reserve amphibious fleet could just as easily be assembled in the northern port of Dailan for, say, a training exercise. In any event North Korea does not appear concerned about this, or any other, threat by China.