North Korea was considered too poor, authoritarian and vulnerable to succeed with its nuclear and missile programs. And yet Pyongyang has acquired advanced nuclear weapons capabilities — and, at the end of November, tested an intercontinental ballistic missile.

Why has North Korea succeeded when other countries such as Iraq and Libya have failed?

Three factors are central to North Korea’s success. This analysis draws on findings about the North Korean program from a recent New York Times article, as well as my recent book on the Iraqi and Libyan nuclear programs.

1. Kim Jong Un made nuclear weapons his top priority.