To the Editor

Christopher Gainor’s useful article “The Atlas and the Air Force: Reassessing the Beginnings of America’s First Intercontinental Ballistic Missile” adds to our knowledge of this program.¹ But his argument lacks a vital prop. The first sentence in Gainor’s conclusion reads: “This study has shown that the U.S. Air Force moved ahead with its first ICBM, the Atlas, in 1954—and not before—because it took the creation of thermonuclear weapons to make ICBMs technically and politically feasible” (p. 363). This has long been the usual understanding.² Yet, Gainor’s account, like others, elides well-documented advances in fission weapons, suggesting that thermonuclear warheads, as opposed to smaller and lighter fission warheads, need not have been critical to the Atlas decision, at least from a technological standpoint.

Gainor argues that the prospect of thermonuclear weapons meant that Atlas could be designed to carry a warhead weighing only 3,000 pounds, while otherwise it would have been “a gargantuan ICBM carrying an 8,000- pound warhead that would have weighed 670,000 pounds, stood 160 feet tall, and required seven rocket engines” (p. 358). He writes that “physicists were confident,” in the aftermath of the first thermonuclear test in 1952, “that a new design would make possible thermonuclear bombs that weighed far less than the fission bombs that had been used in 1945 and built in the seven years that followed” (p. 359). In actuality, fission bombs much lighter and substantially more powerful than those dropped on Japan were in production in 1952; the most compact of these weighed 800 pounds and promised an explosive “yield” comparable to the Hiroshima bomb.³ Others were many times more powerful. The Greenhouse test series of “boosted” warheads conducted in the spring of 1951 validated design principles for the Mark 5 fission warhead that entered the stockpile in mid-1952. As a gravity bomb, the Mark 5 weighed slightly over 3,000 pounds and offered variable yields of up to 120 kilotons (kt); cruise-missile versions came in at 500 pounds lighter.⁴

The question thus becomes whether decision-makers during the early 1950s might have construed fission warheads as viable for a strategic missile like Atlas. This is not a technological question, but a matter of politics and policy. As for ICBMs, long-range bombers like the B-29 (or B-50) and B-52 were designed for strategic missions: to carry heavy payloads long distances, enabling strikes that would ostensibly cripple war-making industrial capacity in the enemy’s homeland. Tactical missions, by contrast, strike military targets like troop and supply concentrations nearer to the fighting front. While some, although not all, of the light and powerful fission warheads designed in the early 1950s were considered tactical weapons, the distinction between strategic and tactical missions is an operational and doctrinal matter—independent, within limits, of technical means. Strategic bombers, including B-17s in World War II and B-52s in the Vietnam War, were sometimes assigned tactical missions, and tactical aircraft—for example, fighter-bombers—can execute strategic missions should appropriate targets be within their range.

Most simply, then, the policy question during the early 1950s can be framed as follows: Might the 120-kt yield of a Mark 5 fission warhead have been viewed as adequate for an ICBM? While the Atlas, as deployed in 1959, carried a 3.75 megaton (Mt) warhead, which was over thirty times more powerful than the Mark 5’s, this simply attests to the availability of megaton warheads by that time. Looking forward in the early 1950s, the issue would have been the expected accuracy of Atlas, or other missile systems of intercontinental range, compared with the accuracy expected of manned bombers carrying fission weapons, which at the time comprised the entire U.S. deterrent capacity.

Early ICBMs were not very accurate. As Gainor points out, the original accuracy requirement for Atlas, 1,500 feet, was later relaxed to one mile (p. 358). Yet, under warfighting conditions, as opposed to practice runs, manned bombers were not very accurate either. The so-called strategicbombing campaigns of World War II...