While China's expanded drills surrounding Taiwan have marked an unprecedented military and political warning against outside interference over the island, they opened a window to gather intelligence for the United States and its allies.
The four days of intense drills last week - and extended manoeuvres this week - provide an opportunity to scrutinise the missiles China would use to drive off foreign militaries intervening in any future invasion as well as its command, control and communications systems, regional diplomats and security analysts say.
