North Korea has pursued an aggressive nuclear program since 1993 when it withdrew from the Nuclear Non-Proliferation Treaty. It has conducted nuclear tests in 2006, 2009, and 2013 in violation of agreements made during negotiations with the United States and other countries through the Six Party Talks process. The current leader, Kim Jong-un, took power in 2011 and oversaw North Korea's nuclear test in 2013 while also consolidating power by killing his uncle. North Korea continues negotiations over its nuclear program but has a history of making agreements then backing out.