The medium-range strategic ballistic missile Pukguksong-2, shown in this undated image, was tested recently at an undisclosed location in North Korea. The North has successfully tested solid-fueled missiles four times. Credit Korean Central News Agency, via European Pressphoto Agency

The medium-range strategic ballistic missile Pukguksong-2, shown in this undated image, was tested recently at an undisclosed location in North Korea. The North has successfully tested solid-fueled missiles four times. Credit Korean Central News Agency, via European Pressphoto Agency