Vice President Pence visited the Korean Demilitarized Zone on April 17, and unexpectedly visited the military demarcation line, a part of the heavily guarded border between North Korea and South Korea. (The Washington Post)

Vice President Pence visited the Korean Demilitarized Zone on Monday, not only warning North Korea that the U.S. “era of strategic patience” with Pyongyang is over, but unexpectedly going all the way forward to the military demarcation line, a part of the heavily guarded border between North Korea and South Korea.

The decision made headlines, with CNN reporting that Pence broke with his security plan by leaving a building known as the Freedom House to move closer to the border and its Military Demarcation Line. Doing so set U.S. troops and security personnel nearby “scrambling,” the news channel reported.

But the Korean Demilitarized Zone (DMZ) has long been visited by senior U.S. officials, including former vice president Joe Biden in 2013 and Secretary of State Rex Tillerson last month. U.S. officials, including Tillerson and former defense secretaries Chuck Hagel and Ashton B. Carter, went farther forward then Pence, entering a building at the border in the “Joint Security Area” where diplomatic negotiations have been held in the past.

Each time, the visits have prompted North Korean soldiers to snap photographs of the visiting Americans — something that is thought to be an effort not only to document the events, but also to intimidate the U.S. officials. For visitors like Tillerson, Hagel and Carter, that has prompted surreal sights in which North Korean troops photograph them through windows of the conference building, almost paparazzi-style.

A North Korean soldier takes a picture of Secretary of State Rex Tillerson from outside a window during his visit to the “truce village” at the border of North Korea and South Korea on March 17. (Pool photo by Yonhap via European Pressphoto Agency)

Defense Secretary Chuck Hagel, left, receives a briefing as a North Korean soldier, right, takes pictures of him through the window of a small conference room at the DMZ on Sept. 30, 2013. (Erin A. Kirk-Cuomo/Defense Department)

Pence’s visit came amid heightened tensions that have included North Korea attempting — and failing — to launch a missile in a test Saturday, and the U.S. Navy sending an aircraft carrier and accompanying ships to the region.

Visitors to the Joint Security Area are typically warned that there has been violence there in the past, including a grisly attack in 1976 in which North Korean soldiers killed U.S. Army Capt. Arthur Bonifas and Lt. Mark Barrett with axes after they attempted to cut down a tree that blocked the view of United Nations observers.

However, the DMZ also is a popular tourist site. It includes both a museum and gift shop on the South Korean side and coin-operated binoculars that can be used to see into North Korea’s hills.

Visitors also are allowed to travel underground into one of several tunnels that North Korean soldiers dug in the 1970s in an attempt to invade South Korea. The South Korean military found the first of them in 1978 and another in 1990.

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