South Korea’s defense minister referred to the possibility of a North Korean military provocation last Tuesday, as he had often done in the past. But this time, he gave a specific time frame. He said the possibility was high that North Korea would provoke the South from late January to early March.

Detractors denounced him for making such a grave comment without providing backup information and, by doing so, fanning fear among the public. His warning, however, deserved keen public attention, given that he was privy to classified intelligence on North Korea’s military activities.

Two days later, South Korea received a confidential fax message from the North, which said Pyongyang would “take a relentless retaliatory action without warning or mercy” if anti-Pyongyang demonstrators in the South continued to vilify Kim Jong-un and his late father, Kim Jong-il.

The warning followed a large protest rally that South Korean conservative groups had launched on the second anniversary of Kim Jong-il’s death on Tuesday. They burned father and son effigies, which the North regarded as an act of sacrilege.

The warning was unconventional in several ways, which should give the South cause for deep concern. It could prove to be a grave mistake for the South to play down the North’s bellicosity, as it did.

First of all, the North sent its telephone message via the western coastal military communication line, in a departure from its usual practice of sending such warnings through its official news media. Another noteworthy feature was that the message, signed by a formidable North Korean agency headed by Kim Jong-un, the National Defense Commission, was addressed to the National Security Council, chaired by President Park Geun-hye.

By going the extra mile in sending the message, did the North mean to say this time was different? Or did it intend to instill greater fear into South Korean society, as some claimed? Either way, Seoul would do well to err on the side of caution, and all the more so, given that Kim Jong-un could still be on edge after recently executing his powerful uncle Jang Song-thaek on charges of treason.

The South sent a reply to the North, vowing to launch “stern retaliation” against any provocations. But this will not be enough. The South will have to take all measures necessary to convince the North that it is both capable of making and ready to make good on its vow to retaliate many times more. There will be no better deterrence to North Korea’s ill-conceived adventurism.