Kim Jong Un has spent much of his time as North Korea's leader developing bigger and more advanced nuclear weapons. This year, he may try to make them harder to find by putting them under the sea.

Recent North Korean reports touting a new submarine and its test of a ballistic missile designed to be launched from one have fueled speculation that a sub may be the "new strategic weapon" Kim promised to unveil this year. While such a vessel would probably be noisy and unable to stray far from the coast without being tracked, it may be enough to serve Kim's needs.

Even one submarine lurking off the Korean Peninsula, beyond the gaze of spy satellites, would give U.S. military planners a dangerous new threat to consider in the event of any conflict. And for Kim, anything that makes it harder for the United States to imagine an actual war brings him closer to a goal that eluded his father: international recognition as a nuclear state.