If all goes according to plan for Kim Jong-il, he will likely announce this week at the third communist party conference that his 27-year-old son, Kim Jong-un, will take over from him. But even under his totalitarian regime, a challenge seems to have emerged from within the party. Chang Sung-taek, Kim Jong-il's powerful brother-in-law, had led an aggressive faction and could figure prominently in any plans for the future amid fears of total collapse in the hands of Kim’s inexperiencd son. "Succession is always the Achilles' heel of regimes like this," said one North Korea expert. Chang might be chosen to act as “regent,” to help the succession period move along smoothly, or even as leader in the event Kim Jong-un proves completely incapable. Chang was purged from the party in 2004 and reinstated two years later and, most importantly, was the man who took control when Kim Jong-il suffered a stroke in 2008.