A portrait is drawn on the side of a community soccer stadium below a blast hole caused by a North Korean shell that was fired at Yeonpyeong Island on Nov. 23, 2010. (Chico Harlan/The Washington post)

North Korea’s fatal artillery attack on this border island more than two years ago uprooted old wooden houses from their foundations. One shell punctured the concrete side of a soccer stadium. Another struck a rooftop oil tank. Residents rushed to underground bunkers, and when they emerged hours later, much of their island was aflame.

Among dozens of North-led provocations against the South over decades, the shelling of Yeon­pyeong — which killed two marines and two construction workers — is far from the deadliest or most audacious. But the attack carries oversize importance as tensions again soar between the Koreas, because it redefined the South’s thinking about how strongly its military should respond if attacked again.

South Korean officials cite ­Yeonpyeong as an instance in which their forces returned fire too late and too timidly — a mistake that they pledge will not be repeated. If faced with a similar attack, President Park Geun-hye has told her military, the South should strike back “without political consideration” and without waiting for top-level approval.

South Korea’s hardened line, analysts say, provides an important backdrop as North Korea threatens the region — and the United States — with nuclear and more small-scale artillery attacks. The prospect of a South Korean counterstrike, the analysts say, might explain why the North hasn’t made good on any of its recent threats. But it also means that if the North does attack, the conflict is far likelier to escalate.

South Korea’s new stance is not just rhetorical. After the Yeonpyeong shelling, Seoul revised its rules of engagement, allowing front-line commanders to “take aggressive action . . . and then report it up the chain of command,” Lee Myung-bak, South Korea’s president from 2008 until this year, recently told a major South Korean daily. Lee added that the United States was initially opposed to the rule changes.

Although the United States has about 80,000 troops in the region, with 28,500 of them in South Korea, it would be up to the South to defend itself in the opening minutes of a North-led attack. Still, Seoul and Washington recently drew up what they call a “counterprovocation” plan that lays out potential responses to North Korean attacks.

The goal of the plan, Adm. Samuel Locklear III, commander of U.S. troops in the Pacific, told Congress last week, is to ensure that responses are “predictable” and to prevent an “unnecessary escalation that none of us want.”

A war zone

A majority of South Koreans support a strong response to any attack from their neighbor, but Yeonpyeong, just seven miles from North Korea, represents the emotional heart of that sentiment. Residents here talk about the North as an archenemy, one overdue for revenge.

“They’re bastards,” said Park Myeong-seon, 68, a grandmother of three. “They attacked civilians.”

Yeonpyeong has long hosted a unit of South Korean marines, and it is heavily fortified with underground bunkers and camouflaged firing areas. But before the shelling, few of the island’s 2,000 residents thought they were under threat. Yeonpyeong was famous because it was so difficult to leave: The daily ferry to the mainland is canceled even in moderate winds.

On the afternoon of Nov. 23, 2010, North Korea briefly turned the island into a war zone. In the span of an hour, according to independent and South Korean government reports, the North lobbed 170 shells and rockets toward the island.

Many fell in the sea, missing their target. But some struck the hillside military areas and the shoreline rows of one-story homes. The municipal loudspeaker system, piped throughout town, urged residents to flee underground.

South Korea’s military on the island didn’t respond until 13 minutes after the attack had started; its heaviest weapons had been facing south, for firing drills, and needed to be turned around. The South eventually fired 80 shells at the North, aiming at its army barracks and command areas. It remains unknown whether the South Korean counterstrike caused any casualties.

The South’s slow response was perplexing because it had been warned of the attack. That morning, Pyongyang had sent a telegram to Seoul saying that its army would not “sit idly by” as South Korean troops shot practice rounds of artillery into contested border waters that the North considers its own.

South Korean officials said later that they didn’t take the warning seriously.

“The content of the warning was almost the same as previous warnings given when we were conducting shooting drills,” then-Defense Minister Kim Tae-young testified to the National Assembly.

Turbulent waters

The waters surrounding Yeonpyeong and several other nearby South Korean islands have become perhaps the Korean Peninsula’s most dangerous place. North Korea disputes the maritime border that zigzags north of the islands and was drawn up unilaterally by a U.N. Command officer at the end of the Korean War. In 1999, the North announced a maritime line of its own — one that digs far deeper into South Korean waters.

Since then, this small slice of the Yellow Sea has been the site of several fatal clashes, with occasional firefights between vessels and the March 2010 torpedoing of a South Korean ship by a North Korean mini-submarine.

Since the Yeonpyeong incident, South Korea has made an effort to bulk up its military strength in the Yellow Sea. It stationed an additional 1,000 marines on ­Yeonpyeong, bringing the contingent’s strength to 3,000. It also created a headquarters office to monitor the islands in the region.

Across the border, North Korean leader Kim Jong Un has since March visited several of the military units that keep watch on the South Korean islands, telling his troops to “drive the enemy into a fire pit if so ordered.”

But South Korean military personnel on Yeonpyeong say they do not pay close attention to media coverage of the broader tensions on the peninsula. They face Internet restrictions during their service time here, and their days are shaped by monotony, not frenzy.

“It feels like I’m living in the past” on the island, said Kim Min-chin, 22, among the handful of air force members stationed here. “After 6 p.m., nothing happens. All the lights are off.”

But Kim added, “If they attack, we are fully prepared.”

It’s only on the two-hour ferry rides to and from the island that the troops get a dose — if they want — of the North’s latest war rhetoric. On a recent trip from the mainland to Yeonpyeong, about 100 marines sat in the lower deck. Two flat-screen televisions showed an afternoon talk show, on which three South Korean professors and one government official discussed whether the North would soon launch a mid-range rocket or carry out an attack.

All but five or six of the Marines were sleeping.

Yoonjung Seo contributed to this report.