As the Army National Guard served as a strategic reserve force for deployed active-duty units, the Air National Guard provided mission support to combat operations in Southeast Asia. Immediately following the Gulf of Tonkin Incident in 1964, the Air National Guard began Operation READY-GO, a four-day mission in which aircraft from 23 states and the District of Columbia flew 4,600 miles using three mid-air refuelings to reach airbases in Spain, France and England. Within an hour of landing in Europe the planes were able to be refueled, armed and ready for combat missions, demonstrating the Air National Guard’s ability to respond to short-notice tasking orders.