Kim Jong Un’s pursuit of nuclear weapons, incendiary rhetoric and odd appearance often cast the North Korean leader as an erratic, even deranged dictator.

Yet analysts and South Korean government officials who track North Korea closely describe Kim as a clever and rational, if brutal, figure who has solidified control over his country since assuming power in 2011.

Developing nuclear weapons that threaten the United States is his insurance policy against being overthrown by a U.S.-led coalition, said Joo Seong-ha, a defector who was imprisoned in North Korea before escaping to South Korea.

A nuclear weapons program is “the most powerful bargaining chip that North Korea has,” said Joo.