The new arrangement, requested by South Korea, delayed transition to South Korean command leadership until Seoul has better military capabilities to counter the kinds of nuclear weapons and missile threats posed by North Korea. Defense Secretary Chuck Hagel and South Korean Defense Minister Han Min-Koo signed the accord at the Pentagon on Thursday, a year after they agreed to review the December 2015 timing of the transfer.
Source: https://in.news.yahoo.com/u-south-korea-delay-shift-war-time-command-233221002.html