China is developing new naval mines, and its unknown if Taiwan or the United States will be able to deal with them. It was a 150 years ago, during the Crimean War, that naval mines were first used. The new weapon had recently been developed in Sweden. Russia bought some of them, and used them successfully to keep British warships away from St Petersburg (on the east coast of the Baltic Sea). Despite their long use, naval mines continue to be formidable weapons that are difficult to deal with. Naval mines have consistently been underestimated. As recently as the 1991 Gulf war, it took coalition naval forces a year to clear ten naval mine fields. During the 2003 Iraq war, coalition forces prevented new mine fields from being laid by quickly seizing the mine laying ships. Also since 1991, the United States has developed many new mine clearing systems, taking advantage of advances in computer, laser and other technologies. However, China is known to be working on new mine designs, while still producing Russian designed mines. 

Its the uncertainty that makes things interesting in wartime. The United States keeps the exact capabilities of its new mine clearing equipment secret. The Chinese are even more secretive about the design of their new naval mines. This is where espionage becomes are real weapon. If either side can get good information on the other sides systems, and especially if they can keep details of their own systems secret, that will produce a substantial advantage during the opening weeks and months of a future war. China, for example, will strive to develop mine sensors that cannot be triggered prematurely by American mine clearing equipment. They can only do that if they know enough details of how that mine clearing gear operates. That equipment expects to encounter certain types of mine sensors, and casings. Create a mine that the mine clearing equipment doesnt recognize, and that mine wont get cleared until a passing ship causes it to explode. 

Naval mines went high tech during World War II, with the development of bottom mines (they sit on the ocean floor) that react to sound or the water pressure created by ships overhead. Mine research slowed down after World War II, but picked up again after a few decades. Now you have some real mystery mines out there. Navies are often reduced to guessing about exactly what they will be up against, and hoping that current mine clearing gear can do the deed.

Naval mines never got much respect. But when a war starts, naval mines always get plenty of attention.