Two years have passed since North Korea shelled the South’s Yeonpyeongdo in the West Sea. The artillery bombardment on Nov. 23, 2010 killed two soldiers and two civilians, injured many others, and devastated villages on the peaceful island.

It was the first attack by the North against civilians in the South since the Korean War ended in 1953. As reasons for its deadly bombing, Pyongyang cited firing drills by the marines on the island. Yet it was nothing more than a thinly veiled pretext for its unwarranted aggression.

Pyongyang’s attack was part of its tenacious efforts to invalidate the Northern Limit Line, the de facto maritime border between the two Koreas drawn by the United Nations Command.

To nullify the line, the bellicose regime has provoked numerous naval clashes around the South’s five border islands of Yeonpyeong, Baengnyeong, Daecheong, Socheong and Wu.

Months before shelling the island, the North torpedoed the South’s Cheonan corvette near Baengnyeongdo, killing 46 sailors on board. It also started the first Battle of Yeonpyeong in 1999, the second one in 2002 and the Battle of Daecheong in 2009.

All these attempts have failed. Yet Pyongyang has not given up. Rather, in the two years since the Yeonpyeong shelling, it has beefed up its combat forces and firepower near the NLL, threatening to stage more serious provocations.

Early this year, the North built a large-scale pier in Goampo, South Hwanghae Province, that can accommodate 70 hovercraft. These vessels are armed with torpedoes and machine guns and have a top speed of almost 100 kilometers per hour.

According to reports, it would take a mere 17 minutes for these high-speed boats to reach Baengnyeongdo from their newly built base.

Pyongyang has also deployed more than 50 attack helicopters to its air bases close to Baengnyeongdo. To reinforce its firepower, it forward deployed upgraded 240-mm multiple rocket launchers.

While building up its combat power, the North has staged war games more frequently. Between May and August, it conducted a series of landing operations involving land, naval and air forces at an island near the NLL. It also carried out maritime infiltration drills using submersible vessels.

All these moves suggest the North’s military might be plotting to raid and occupy one of the five border islands.

To prepare for the North’s possible provocations, Seoul has reinforced the defense capabilities of the troops on the frontline islands. It has deployed more AH-1 Cobra attack helicopters, K-9 self-propelled guns and counter-battery radars that automatically locate enemy artillery.

The South’s military has also conducted drills in anticipation of the North’s attempts to invade the border islands.

Yet Seoul’s defense posture has loopholes that need fixing. Following the Yeonpyeongdo fiasco, the government decided to procure precision strike missiles from Israel to cripple the North’s coastal artillery guns. Yet the plan has been delayed.

The Army’s program to purchase tethered aerostats from the United States is also behind schedule. Equipped with radars, the moored balloons are used for various surveillance tasks.

The Navy has sought to deploy unmanned aerial vehicles to provide image data to its intelligence ships operating near the border islands. Yet this scheme also suffers a delay.

More importantly, despite the build-up of firepower, the three relatively smaller islands ― Daecheong, Socheong and Wu ― still remain vulnerable to the North’s possible occupation attempts as they have only a small or no marine unit stationed.

As the December presidential election approaches, the possibility of Pyongyang staging fresh provocations is looming increasingly large. Defense Minister Kim Kwan-jin warned Thursday that the North might provoke the South before or after the election.

Kim said Pyongyang could attempt a provocation before the election to make it a choice between war and peace. It could also provoke Seoul after the vote to test the new government.

Foreign Minister Kim Sung-hwan sounded a similar warning, noting Pyongyang’s track record of testing each new government in Seoul after a presidential election.

While Pyongyang is determined to have the NLL abolished, political leaders in the South have made it an object of political controversy. This is a recipe for disaster. It would only justify the North’s provocations. To avert them, political leaders should have behaved more responsibly in the first place.