In preparation for his upcoming high-stakes summit with U.S. President Donald Trump, North Korean leader Kim Jong Un has made a second unexpected visit to China. Kim traveled by airplane to the northeastern Chinese city of Dalian for a two-day stay from May 7 to 8, reportedly accompanied by his sister Kim Yo-jong. He met with Chinese President Xi Jinping, who was already scheduled to travel to Dalian for a sea trial of China's first domestically built aircraft carrier, as well as Chinese Foreign Minister Wang Yi and Politburo Standing Committee member Wang Huning....