Pressure between China and Taiwan has been building, with the past year seeing a record number of Chinese warplane incursions sent into Taiwan's air defence zone. At the heart of this is the issue of reunification. China's President Xi Jinping has said "reunification" with Taiwan "
must be fulfilled" - and has not ruled out the possible use of force to achieve this. China sees self-ruled Taiwan as a breakaway province that will eventually be part of the country again.