Classical unified field theories describe the properties of the electromagnetic field as a purely geometric phenomenon. Einstein tried to form a generalized theory of gravitation that would unify the gravitational and electromagnetic forces (and perhaps others), guided by a belief in a single origin for the entire set of physical laws. These attempts initially concentrated on additional geometric notions such as vierbeins and "distant parallelism", but eventually centered around treating both the metric tensor and the affine connection as fundamental fields. (Because they are not independent, the metric-affine theory was somewhat complicated.) In general relativity, these fields are symmetric (in the matrix sense), but
Unified combatant command also existed to coordinate British and American military forces operating under the Combined Chiefs of Staff, which was composed of the British Chiefs of Staff Committee and the American Joint Chiefs of Staff. In the European Theater, Allied military forces fell under the command of the Supreme Headquarters Allied Expeditionary Force (SHAEF). After SHAEF was dissolved at the end of the war, the American forces were unified under a single command, the US Forces, European Theater (USFET), commanded by General of the Army Dwight D. Eisenhower. Unified commands in the Pacific Theater proved more difficult to organize as neither General