Low-level border skirmishes across the demilitarized zone and particularly the NLL are not uncommon even at the scale of artillery fire. In March, the South Korean naval corvette ChonAn was sunk in the area by what is broadly suspected to have been a North Korean torpedo, taking tensions to a peak in recent years. Nov. 22 also saw South Korean rhetoric about accepting the return of U.S. tactical nuclear weapons to the peninsula, though the United States said it has no plans at present to support such a redeployment.

While the South Korean reprisals — both artillery fire in response by self-propelled K-9 artillery and the scrambling of aircraft — thus far appear perfectly consistent with South Korean standard operating procedures, the sustained shelling of a populated island by North Korea would mark a deliberate and noteworthy escalation.

The incident comes amid renewed talk of North Korea’s nuclear program, including revelations of an active uranium-enrichment program, and amid rumors of North Korean preparations for another nuclear test. But North Korea also on Nov. 22 sent a list of delegates to Seoul for Red Cross talks with South Korea, a move reciprocated by the South, ahead of planned talks in South Korea set for Thursday. The timing of the North’s firing at Yeonpyeongdo, then, seems to contradict the other actions currently under way in inter-Korean relations. With the ongoing leadership transition in North Korea, there have been rumors of discontent within the military, and the current actions may reflect miscommunications or worse within the North’s command-and-control structure, or disagreements within the North Korean leadership.