in august 1998, the air force inaugurated a new concept. based on experiences during the persian gulf war and numerous deployments to the balkans and other contingency operations, it organized more than 2,000 aircraft, including those of air force reserve and air national guard units, into 10 air expeditionary forces (aefs), later designated as the aerospace expeditionary forces, and, in 2007, the air and space expeditionary forces. aefs would rotate in order to ease the strain of increased post-cold war operations overseas. the aef promised to spread the burden of deployments more widely among flying units, active duty, air force reserve or air national guard. moreover, the timing of rotations became more predictable. greater predictability would enable airmen, especially those in the air reserve component, to better manage the competing demands of families, civilian careers, and military service. air national guard aviation units would be expected to deploy overseas once every 15 months while support units would do so at 30-month intervals. driven by those requirements, air national guard planners in the national guard bureau began to "reengineer" ang units to better participate in their expeditionary roles. the benefits of this concept became apparent in the events of the early 2000s.