Army AirLand Battle Doctrine is based on securing or retaining the initiative and exercising it aggressively to accomplish the mission. In the aftermath of the Vietnam War, the services, particularly the Army, had to recover, reorganize, rebuild, and rethink the conduct of war and military professionalism. Recovery required time, tenacity, intelligence, money, a vision of the future, the right political environment, and love of service and country. In the aftermath of the Vietnam War, some argued that strategic bomber doctrine had undergone a stealth and precision "revolution". In the 1990s, two new aircraft were revealed to the world: the F-117 stealth fighter and the B-2 stealth bombers. These aircraft were capable of penetrating enemy air space undetected by radar, and they employed precision weapons. The new doctrine of strategic bombing applied precision weapons to the enemy's strategic centers of gravity.