The small island group of MATSU was subject of both of the 1950s' Taiwan Straight Crisis. Though much closer to mainland China, the islands have since 1949 belonged to Taiwan. During intense military confrontation they served as Taiwan's first line of defence and were target of People's Republic Artillery Bombardement.
Cross strait relations have greatly improved since then, yet the islands are essentially still Taiwanese military bases, illustrating how islands in the East China Sea tend to be more than just "fishing islands".
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