Taiwan has reported the largest incursion since October by China’s air force into its air defence zone, with the island’s defence ministry saying Taiwanese fighters scrambled to warn away 39 aircraft in the latest uptick in tensions. Taiwan calls China’s repeated nearby military activities “grey zone” warfare, designed to both wear out Taiwan’s forces by making them repeatedly scramble, and also to test Taiwan’s responses. Al Jazeera reports that there was no immediate comment from China, which has in the past said such moves were drills aimed at protecting the country’s sovereignty, but China has recently stepped up pressure on Taiwan to accept its sovereignty claims.