The new tank destroyer doctrine was formally stated in Field Manual 18–5, "Tactical Employment, Tank Destroyer Unit", in June 1942. It laid down a focused doctrine— "There is but one objective of tank destroyer units… the destruction of hostile tanks" —and repeatedly emphasized an offensive, vigorous spirit. Tank destroyer units were expected to be employed as complete battalions, held in reserve and committed at critical points, rather than parceled out as small defensive strongpoints. The emphasis was heavy on mobility, and the ability to outmaneuver the attacking armor; this would feed into vehicle design, and cause the speed of a vehicle to be prioritized over survivability.