[5] In 1942, Barth was hand picked by Lieutenant General Frank Maxwell Andrews to serve as the Assistant Chief of Staff, G-4, of the U.S. Army Forces in the Middle East.

He remained in this role until 1943, where he would follow Andrews to London to the European Theater of Operations, United States Army, where he served as the chief of staff.

In 1943, Andrews was summoned to Washington, D.C., by General George C. Marshall, the Chief of Staff of the United States Army.

Barth went with him, the two hitching a ride with Hot Stuff (aircraft), a heavy bomber that was returning to the United States to complete a morale tour to help sell war bonds.

On 3 May 1943 the flight crew had attempted to stop and land in Reykjavik, Iceland to refuel, however due to poor weather conditions they could not locate the runway.