A brigade of the army under the Eastern Theater Command and a department of the Navy carry out a multi-subject combat training in a sea area in Zhangzhou, Fujian province, China, Aug 27, 2022.CFOTO/Future Publishing via Getty ImagesNaval mines could be a cheap but useful addition to Taiwan's defenses.Experts have argued that for Taiwan to develop a "porcupine" strategy, and mines could be key.