In accordance with the experience of World War I, it was usually conceived of as a large land mass over which continuous operations would take place and was divided into two chief areas-the combat zone, or the area of active fighting, and the Communications Zone, or area required for administration of the theater. The term theater of operations was defined in the US Army field manuals as the land and sea areas to be invaded or defended, including areas necessary for administrative activities incident to the military operations. It was bordered to the south by the North African Theater of Operations, United States Army (NATOUSA), which later became the Mediterranean Theater of Operations, United States Army (MTOUSA). It commanded Army Ground Forces (AGF), United States Army Air Forces (USAAF), and Army Service Forces (ASF) operations north of Italy and the Mediterranean coast. The European Theater of Operations, United States Army ( ETOUSA) was a Theater of Operations responsible for directing United States Army operations throughout the European theatre of World War II, from 1942 to 1945.

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