During the Vietnam War much of the US air power had been directed against supply buildup and movement points; roads, bridges, supply depots and the like. Attacking these targets with conventional weapons was an expensive process, requiring considerable amounts of ordnance to be expended to guarantee a "hit". In the late 1960s and early 1970s the introduction of smart weapons allowed conventional forces to directly attack point targets like bridges and roads, dramatically improving the ability to interdict the enemy, while at the same time allowing the aircraft to operate from safer, higher altitudes. These had little real impact during Vietnam when they were still very new, but their potential was obvious.