 The most obvious of these were the antiaircraft artillery (AAA) battalions created to defend Washington, D.C., and Hampton Roads from air attack.Initially armed with guns firing "flak" these were, in the mid-1950s, replaced by Nike missiles capable of destroying enemy aircraft before they could hit their targets.And the structure of the state force expanded beyond only combat arms to include specialized support units including military police, medical, transportation, engineers, signal, data processing and even a military history detachment.