For more than a half century, this divided hamlet has been the front-line of a fragile truce that ended the three-year Korean War. Intimidation has been honed to a fine art here. But while tensions this week rose to their highest level in years, there was an odd sense of calm in the Demilitarized Zone.

Skirmishes have a tendency to escalate quickly in Panmunjom.

An effort by American soldiers to trim a popular tree led to an ax fight with North Koreans in 1976 that left two dead. An attempt by a Russian to defect across the demarkation line in the 1980s sparked an extended shootout.

But no incidents have been reported here recently, despite North Korea‘s nuclear test, a week of missile launchings and repeated tirades from Pyongyang that it will no longer abide by the 1953 accord that ended the war.

“We are always at a high level of readiness, but nothing has changed recently,” said U.S. Army Sgt. Brant Walker, part of the small contingent of U.S. troops that are based along the heavily fortified border. “You wouldn’t think it would be, with North Korea right there, but it’s very relaxed.”

Outside of the Demilitarized Zone, however, concerns swirled around the North as spy satellites spotted signs that it may be preparing to transport a long-range missile to a test launch site, South Korean officials said Saturday.

U.S. Defense Secretary Robert Gates issued his harshest warning to the North since it carried out an underground nuclear test on Monday.

“We will not stand idly by as North Korea builds the capability to wreak destruction on any target in Asia — or on us,” he told a regional defense meeting in Singapore. He said the North’s nuclear program was a “harbinger of a dark future,” but wasn’t yet a direct threat.