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The fortress island fixed in North Korea's sights

Ian Williams/ NBC News

Shell-encrusted beach defenses - large metal spikes embedded in concrete to obstruct landings – stand on the beaches of South Korea's Baengnyeong Island.  The small island is South Korea's northernmost island and sits quite literally in North Korea's crosshairs.

BAENGNYEONG ISLAND, South Korea -- On the face of it there's nothing particularly exceptional about the Harmony Flower, a black and yellow 565-seat ferry that leaves the South Korean port of Incheon at 8.50 a.m. every day, heading northwest into the Yellow Sea.

Hikers in bright windproof jackets sit amid school children returning to their island home after a field trip to the mainland. A group of elderly Koreans settles in a circle on the floor for a game of cards.

Yet this must be one of the most precarious ferry routes in the world, plying the waters between two states still technically at war, and where the rhetoric from North Korea has raised tensions to levels not seen in years.

The Harmony Flower skirts North Korean territory, cruising beside disputed waters on its four-hour journey from Incheon to Baengnyeong, South Korea’s northernmost and most isolated island.

It's a sunny day, but cold, and with a bitter wind. A few hardy travelers brave the outside deck as the craggy outline of Baengnyeong comes into view through the early afternoon haze.

Baengnyeong, a 20-square-mile island, sits quite literally in North Korea’s crosshairs.

Baengnyeong is South Korea's northernmost and most isolated island. Since 1999, the island has been the scene of the most military incidents between the two Koreas. NBC News' Ian Williams takes viewers on a tour of the island.

Since 1999, this area has been the scene of most military incidents between the two Koreas. The North’s mainland looms to the east and north of Baengnyeong. At its closest point, it is just ten miles away.

Some 5,000 people live on Baengnyeong with roughly the same number of South Korean soldiers.

"The soldiers are quite tense at the moment," said Hong Sang Chul, a driver, fisherman, shop owner and occasional tour guide, as they watched us from high of the island's watchtowers.

Local people have been told to keep off the beach after dark, but at low tide during daylight hours they take tunnels through the wall to collect mussels off the shell-encrusted beach defenses – large metal spikes embedded in concrete to obstruct landings.

Sea of fire
The disputed waters used to be a popular fishing ground, naturally replenished during times of tension when the fishermen stayed at home. Recently Chinese boats have been coming in growing numbers.

“There are usually around two to three hundred Chinese fishing boats out there,” Hong said. “But a week ago they all left. They decided it was too dangerous to fish here.”

Baengnyeong is like a fortress, the coast lined with tall concrete walls, 30 feet thick in places and topped by layers of razor wire. It’s punctuated with watch towers every few hundred feet.

Ian Williams / NBC News

Baengnyeong is like a fortress, the coast lined with tall concrete walls, thirty feet thick in places and topped by layers of razor wire. It's punctuated with watch towers every few hundred feet.

Radar stations sit on top of the hills to give early warning of any North Korean attack, and red signs warn of coastal mine fields.

On top of one hill is a vantage point overlooking North Korea, beside which sit a decommissioned tank and a gun emplacement. A sign beside the gun informs that it has a range of 15 miles.

These weapons are for the benefit of visitors; the serious and more modern weaponry is hidden.

North Korea's young leader Kim Jong-un has issued almost daily threats, including the threat of nuclear strikes on Washington, D.C., and Seoul. In addition, Pyongyang has put its troops on combat readiness, warning that war "may break out at any moment." NBC's Ian Williams reports.

Earlier this month, the North Korean dictator was shown on television inspecting a missile base, and peering through binoculars at Baengnyeong. He threatened to turn it into a sea of fire.

“He was over there, that’s where Kim Jong Un was standing,” said Hong, pointing a small island, just off the main North Korean coast.

A little further round the coast is a large memorial to 46 sailors who died three years ago in the sinking of a South Korean patrol boat, the Cheonan, a little over a mile from the coast here, the apparent victim of a North Korean torpedo attack.

Another island, Yeonpyeong, to the south of here, was attacked that same year with a sudden barrage of artillery from the North that killed four people and injured 44 others. Both attacks came without warning.

South Korea, with a new and more hard-line president, has vowed to hit back hard and is unlikely show the same restraint as last time.

Hong has lived through years of threats and theatrics. But this ratcheting up of tensions feels new.

“Of course it worries me,” he said. "I am worried."

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