Classical unified field theories to isospin rather than electromagnetism; this is related to a discrete (or ""internal"") symmetry known to Einstein as "displacement field duality". Einstein became increasingly isolated in his research on a generalized theory of gravitation, and most physicists consider his attempts ultimately unsuccessful. In particular, his pursuit of a unification of the fundamental forces ignored developments in quantum physics (and vice versa), most notably the discovery of the strong nuclear force and weak nuclear force. Inspired by Einstein's approach to a unified field theory and Eddington's idea of the affine connection as the sole basis for differential geometric structure for space-time,
Unified combatant command the terms of Article II of the United States Constitution. Thereafter, the military CINCs would be known as "combatant commanders", as heads of the unified combatant commands. A sixth geographical unified command, United States Africa Command (USAFRICOM), was approved and established in 2007 for Africa. It operated under U.S. European Command as a sub-unified command during its first year, and transitioned to independent Unified Command Status in October 2008. In 2009, it focused on synchronizing hundreds of activities inherited from three regional commands that previously coordinated U.S. military relations in Africa. President Donald Trump announced on 18 August 2017 that