Taiwan believes that since 2009 China has maintained a force of at least 1,400 ballistic missiles aimed at them. That's up from 200 in 2000, 800 in 2004 and 1,300 in 2008. Most of these are Dong Feng DF-11 and DF-15 models. The DF11 (also known as the M11) has a range of 300 kilometers and carries a one ton warhead. The DF15 (M9) has a range of 600 kilometers and carries a half ton warhead. From the Chinese coast, to targets in Taiwan, it's about 200-300 kilometers across the Taiwan Straits.
In addition to the ballistic missiled there are also over a thousand Chinese warplanes and over 100,000 troops (including several brigades of paratroopers) available for an attack on the island. The missiles would use high explosive or cluster bomb warheads, and would basically be bombs that could not be stopped. Well, that's not exactly the case. Taiwan is investing in an anti-missile system that would negate a large number of the Chinese missiles.
If used, perhaps 75 percent of the missiles would actually hit their target. The others would suffer failures in propulsion or guidance systems. Each missile is the equivalent of a half-ton or one ton aircraft bomb. But currently, the missiles have primitive guidance systems, meaning that the warheads will usually hit up to 500 meters from the target. The Chinese are believed to be equipping the missiles with GPS, although the Taiwanese can jam this. Guidance systems that are more difficult to jam are in the works, as this technology has been much sought after by Chinese spies in the United States over the last few years.
Since 2010 China has also been increasing its missile forces aimed at American and Japanese forces in the region. Japan would simply have several hundred ballistic missiles moved to parts of China close enough for these missiles to hit Japanese military bases. Crippling American forces in the west Pacific was another matter especially since the Chinese don’t want to use nukes, or pay a lot more for hundreds of expensive longer range ballistic missiles carrying high-explosive, instead of nuclear, warheads.
Another problem was the American fleet. But by 2013, after a decade of effort, American naval intelligence believed China had developed a working version of a ballistic missile that could hit a moving aircraft carrier. This is the DF-21D. The basic DF-21 is a 15 ton, two stage, solid fuel missile that is 10.7 meters (35 feet) long and 140cm (4.6 feet) in diameter. Range varies (from 1,700-3,000 kilometers) depending on model. The DF-21D is believed to have a range of 1,500-2,000 kilometers. While the 500-2,000 kg (.5-2 ton) warhead usually contains a nuclear weapon, there are also several types of conventional warheads, including one designed for use against warships. Some of these conventional warheads are for use against targets in Taiwan. This is because the DF-21, as a longer range ballistic missile that comes down on the target faster than the shorter range ballistic missiles aimed at Taiwan. That means that the DS-21 is too fast for the Pac-3 anti-missile missiles Taiwan is installing around crucial installations.
Until 2013 there was no evidence that the complete DF-21D system had been tested. But in 2013 satellite photos showed a 200 meter long white rectangle in the Gobi Desert (in Western China) with two large craters in it. This would appear to be a “target” for testing the DF-21D, and two of the inert practice warheads appear to have hit the target. American carriers are over 300 meters long, although the smaller carriers (amphibious ships with helicopter decks) are closer to 200 meters long. It appears China is planning on using the DF-21D against smaller warships, or perhaps they just wanted to see exactly how accurate the missile could be.
Between 2010 and 2013 various components of the DF-21D were tested, but until these satellite photos showed up there was no evidence that there had been any tests of the complete system against a carrier size target. Since 2011 there have been photos of DF-21Ds on TELs (transporter erector launcher vehicles), and announcements of the first units activated in 2010. Then in 2013 came some tests. What has not been done at that point was a “dress rehearsal” test against a large ship (an old tanker or container ship would do) at sea and moving. That has yet to happen. But DF-21Ds on TELs were publicaly displayed in a September 2015 parade.
Meanwhile, China has three "remote sensing" satellites in orbit, moving in formation at an altitude of 600 kilometers across the Pacific. Equipped with either radar (SAR or synthetic aperture radar) or digital cameras, these three birds can scan the ocean for ships, even though the Chinese say their purpose is purely scientific. A typical SAR can produce photo quality images at different resolutions. At medium resolution (3 meters) the radar covers an area 40x40 kilometers. Low resolution (20 meters) covers 100x100 kilometers. This three satellite Chinese posse looks suspiciously like a military ocean surveillance system. This is the missing link for the Chinese ballistic missile system designed to attack American aircraft carriers.
China has been developing the DF-21D, or key components of it, since about 2001. Most of the development effort was devoted to targeting systems that would enable them to seek out and find aircraft carriers. On the DF-21D warhead itself, sensors would use infrared (heat seeking) technology for their final approach. This sort of thing had been discussed for decades, but China appears to have put together tactics, sensors, and missile systems that can make this all happen. The key was having multiple sensor systems which would include satellites, submarines, or maritime patrol aircraft that could find the general location of the carrier before launching the ballistic missile. Those sensors appear to be operational, as is the DF-21D itself.