After North Korea’s missile launch on April 13, 2012, uncertainty in the security environment on the Korean peninsula is at its height. Therefore, it is timely and important to examine potential military threats from North Korea and the countermeasures that the ROK and the US should prepare. This paper aims at studying the nature of North Korea’s military threats and various types of provocations and analyzing ROK-US cooperation to deter North Korea’s provocative actions. First, this paper points out that North Korea has been utilizing provocations to help secure its regime survival, and presents the escalatory nature of North Korean military provocations. Next, it examines changes of North Korea’s strategy and analyzes North Korea’s military options. It categorizes various aspects of North Korea’s provocations according to the type (non-collision and collision) and the level (low-intensity and high-intensity) of incidents. Lastly, this paper addresses the issues of extended deterrence and stressed ROK-US cooperation with policy suggestions for the ROK and the US.