By the 1950s, around 5,500 targets were listed to receive SAC bomber strikes; these targets consisted primarily of industrial sites but included counterforce targets. These plans, primarily by the Air Force, tended to be based on selecting targets in order to use up the available weapons, rather than considering the desired effects or strategic outcomes. From a 1957 letter from John H. Moore, former director of nuclear planning, air operations branch, United States European Command, Air Force target planning methodology can be inferred "blast damage frame," with such references as "damage to concrete structures" and the requirement for a "high probability of cratering runways." He cited the "destructive and disruptive nature of nuclear weapons" with megaton yields: "the cumulative or ancillary effects may be as great or greater than primary damage." Specifically, he considered delayed radiation but not thermal effects, but called attention to the idea of "bonus" effects, in which the totality of weapons effects would allow lower-yield weapons to achieve the "desired destruction." In the letter to the head of the Atomic Energy Commission, Lewis Strauss, Moore noted that the Pentagon "rigorously suppressed" this study and destroyed all copies.