Chinese President Xi Jinping and U.S. President Donald Trump held a phone call touching on the Taiwan question on Monday. That was followed by President Trump and Japanese Prime Minister Sanae Takaichi holding their first phone call since the Japanese PM sparked a major diplomatic fallout with China over her remarks on Taiwan. Beijing has issued a series of strong and coordinated diplomatic responses over Takaichi's refusal to retract her Taiwan remarks, with China's Foreign Minister Wang Yi warning that Japan has "crossed a red line." How seriously has Japan miscalculated China's red lines? And what do these developments mean for regional stability and world order?