For the last three years, the U.S. has refused to sell Taiwan aircraft weapons that could be used to attack China. In particular, this means no radar homing (AGM-88C HARM) missiles and JDAM smart bombs. To get around this refusal, Taiwan has been building their own version of the American JSOW (Joint Stand Off Weapon) Also called the AGM-154A, the Taiwanese version is called the Wan Chien. Taiwan has recently announced it is building its own version of JDAM.
JSOW is basically a smart bomb with wings. That enables it to glide up to 70 kilometers from the aircraft dropping it, to a target on the ground. Range is about 25 kilometers if dropped from low altitude. JSOW also contains more elaborate fins and software that enables it to follow a specific route. Like the wingless JDAM smart bomb, JSOW uses GPS and inertial guidance (as a backup) to find its target. Like JDAM, JSOW hits within 30 feet of its aiming point. The U.S. pays about $250,000 for each JSOW. The Taiwanese could use their Wan Chien. JSOW as a form of HARM to take out the latest Chinese air defense radars, by adding additional sensors to the guidance system.
Taiwan is also building its own version of HARM, called Tien Chien 2A. JDAM technology is a lot simpler than these two other projects, and Taiwan could easily design and build its own. Refusing to sell them just costs the U.S. export sales. On the other hand, it allows the United States to tell China that it didn't sell JDAM to Taiwan, thus defusing tensions over Taiwan. In reality, of course, Taiwan just built their own JDAM.
JDAM (Joint Direct Attack Munitions, or GPS satellite guided bombs) were developed in the U.S. in the 1990s, shortly after the GPS network went live. In 1991, the GPS system was just coming into service. There were already plans for something like JDAM, but no one was sure that it would work. Once the engineers got onto it, it was discovered that JDAM not only worked, but cost less than half as much to build ($18,000 per bomb) as the air force expected ($40,000 a bomb). The current price is still under $30,000 each.
JDAM was a "kit" that attached little movable wings, along with batteries and a GPS guidance unit, to a normal "dumb" bomb. This enabled the JDAM to hit a target with great precision. The technology was off-the-shelf, so the Taiwanese had no problems developing and building their own.
In 1996, production of U.S. JDAM began. The bombs got their first workout in the 1999 Kosovo campaign. To everyone's surprise, 98 percent of the 652 JDAMs used, hit their targets. In 2001, JDAM proved the ideal weapon for supporting the few hundred Special Forces and CIA personnel the U.S. had on the ground in Afghanistan. The JDAM was more accurate, and effective, than anticipated. By January, 2002, the U.S. had dropped about half their inventory, of 10,000 JDAMs, in Afghanistan.