When South Korea's President Park Geun-hye welcomes Xi Jinping to the Blue House today, it will mark the first time that a Chinese leader will visit Seoul without having first visited Pyongyang.
This is a remarkable development when one considers the close ideological and historic ties between China and North Korea, but it would be premature to assume that Beijing has abandoned Pyongyang for Seoul.
China under Mao Zedong saved Kim Jong-un's grandfather from certain defeat at the hands of UN forces led by General MacArthur during the 1950-1953 Korean War (still known in China as the "War to Resist US Aggression and Aid Korea") by preventing the advance of allied forces to the China-North Korean border at the Yalu River and fighting to a stalemate.
Although North Korea saw China's normalisation of relations with South Korea in 1992 as a betrayal, and Sino-South Korean trade is now almost 40 times larger than its trade with North Korea, China has not allowed its 1961 security commitment to North Korea to lapse. Neither has Beijing withdrawn its extensive economic assistance or political support for North Korea.
Even in the aftermath of North Korea's 2010 shelling of South Korean islands, Beijing protected North Korea from international condemnation of those actions at the United Nations.