China is having problems with its JL (Julang) 2 SLBM (Sea Launched Ballistic Missile). The 42 ton JL-2 has a range of 8,000 kilometers, and would enable China to aim missiles at any target in the United States from a 094 class SSBN (ballistic missile carrying nuclear subs) cruising off Hawaii or Alaska. Each 094 boat will carry twelve of these missiles, which are naval versions of the existing land based 42 ton DF-31 ICBM. The JL-2 was supposed to have entered service two years ago, but it is still failing test launches.
Meanwhile, there are at least two 094 class SSBN in service. The 094 is similar to the 093 class SSN (nuclear attack sub), which looks a lot like the three decade old Russian Victor III class SSN design. Taking a SSN design and adding extra compartments to hold the ballistic missiles is an old trick, pioneered by the United States in the 1950s to produce the first SSBNs. The Chinese appear to have done the same thing with their new SSN, creating a larger SSBN boat of 9,000 tons displacement. Priority was apparently given to construction of the 094, as having nuclear missiles able to reach the United States gives China more diplomatic clout than some new SSNs.
There are three more 094s under construction, but they are not much good unless their JL-2 missiles are ready for deployment. Things can go wrong while developing SLBMs, as the Russians learned with their latest SSBN design (the Borei). The Russian SLBM originally designed for the Borei did not work, and a new one (the Bulava), based on a successful land based ICBM (the Topol series) was used instead. But this required rebuilding of the missile tubes in the new subs, thus delaying construction. Then they found that the Bulava did not work very well. While the land based version was quite reliable, the modifications necessary to turn it into the Bulava introduced a lot of failures.
China is now having similar problems with its JL-2. The final round of tests revealed several problems, and the missile has not been working when launched. Unlike the Topol/Bulava, the land based DF-31 the JL-2 was based on was not particularly reliable. This appears to be one of the causes of the problems with the JL-2. As a result of these problems, and perhaps others with the SSBNs, there were no Chinese SSBN patrols last year.