The 6933rd Electronic Security Squadron was a signals intelligence unit of the United States Air Force. During the Cold War, the US military established the Karamürsel Air Station, just outside the village of Karamürsel, Turkey. The Station was located on the Sea of Marmara and was originally built by the German Luftwaffe during World War II. The USAF opened the Station in 1957 in support of the 6933rd Radio Group Mobile communications operations and designated it Detachment 3 of The United States Logistics Group(TUSLOG). It was also known as Mainsite, as it exercised administrative control over at least two other sites designated Det 3-1 and Det 3-2. The site remained in operation until the late 1970s.