Story highlights Journalists with Pence were required to keep his visit secret until his trip back

The secrecy shows how unstable security remains after 16 years of war

Bagram Airfield, Afghanistan (CNN) After 16 years of war, the vice president of the United States still has to sneak onto the largest US military base in Afghanistan.

It was 7:16 p.m. local time when Vice President Mike Pence landed here on Thursday. But the unmistakable blue and white Boeing 757 streaked with the words "UNITED STATES OF AMERICA" that typically announces Pence's arrival was nowhere to be found.

Instead, a windowless, dark gray C-17 military transport plane inconspicuously taxied down the runway before coming to a stop and allowing its precious cargo to step off and become the highest-ranking Trump administration official to visit an active US combat zone. For the next six hours, the dozen journalists traveling with Pence -- including this reporter -- were required to keep his visit secret, until he was prepared to fly back to Washington.

Forty hours earlier, the dozen of us who were scheduled to travel with Pence to Israel and Egypt -- before that trip was postponed -- walked into the vice presidential offices in the Eisenhower Executive Office Building adjacent to the White House. The vice president's communications director, Jarrod Agen, closed the doors and told reporters that everything he was about to say was strictly off the record, confidential information.

Pence was making a secret visit to Afghanistan the next day, his first as vice president, Agen told us, and we were invited to come along. We could tell only one higher-up at each of our news organizations, and if news of Pence's visit leaked, the trip would be canceled altogether because of the security risk.

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