The period from 1939 to 1945 represented the acme of the old style of war, and with it strategy as the purposeful practice of matching military might with political objectives. In its aftermath a number of challenges to this classical paradigm of war emerged, the first in the closing days of World War II. The dropping of atomic bombs on Hiroshima and Nagasaki, Japan, inaugurated a new era of war, many observers felt. Bernard Brodie, an American military historian and pioneering thinker about nuclear weapons, declared in 1946:

Thus far the chief purpose of our military establishment has been to win wars. From now on its chief purpose must be to avert them. It can have almost no other useful purpose.

If that were indeed the case, a strategic revolution would have occurred.

In some ways, nuclear weapons merely made effective the earlier promise of air power—overwhelming violence delivered at an opponent’s cities, bypassing its military forces. Nuclear weapons were different, however, in their speed, their destructiveness, and the apparent absence of countervailing measures. Furthermore, the expense and high technology of nuclear weapons suddenly created two classes of powers in the world: those who wielded these new tools of war and those who did not.

In the ensuing decades, nuclear facts and nuclear strategy had a peculiarly uneasy coexistence. Many of the realities of nuclear weapons—how many were in each arsenal, the precise means for their delivery, the reliability of the devices themselves and of the planes, missiles, and crews that had to deliver them—were obscure. So too were the plans for their use, although a combination of declassification of early U.S. war plans and the flood of information that came out of the Warsaw Pact countries following the collapse of the Soviet Union in 1991 illuminated some of the darkness.

Nuclear strategic thought, however, was far less murky. Those who developed it stemmed less from the military community (with a few exceptions, such as French Gen. Pierre Gallois) than from the civilian academic world and less from the discipline of history than from economics or political science. An elaborate set of doctrines developed to explain how nuclear strategy worked. One such doctrine was “mutual assured destruction” (MAD), the notion that the purpose of nuclear strategy was to create a stable world in which two opponents would realize that neither could hope to attack the other successfully and that in any war both would suffer effective obliteration.

In all cases, the centre of gravity lay with the problem of deterrence, the prevention of adverse enemy behaviours rather than concrete measures to block, reverse, or punish them. Strategic thought now entered a wilderness of mirrors: What behaviour could be deterred, and what could not? How did one know when deterrence had worked? Was it bad to defend one’s population in any way—with civil defense or active defenses such as antiballistic missiles—because that might weaken mutual deterrence? The problem became more grave as additional countries acquired nuclear weapons: Were Chinese leaders deterred by the same implicit threats that worked on U.S. and Soviet leaders? For that matter, did Indians and Pakistanis view each other in the same way that Americans and Soviets viewed each other?

It is likely (although in the nature of things, unprovable) that the looming presence of nuclear weapons prevented a U.S.-Soviet conflict during the Cold War. On the other hand, the highly probable possession of nuclear weapons by Israel in 1973 did not deter an Egyptian-Syrian conventional assault on that country, nor did Britain’s nuclear arsenal prevent Argentina from invading the Falkland Islands in 1982 (see Falkland Islands War). For that matter, North Vietnam seems to have disregarded American nuclear weapons during the Vietnam War (1954–75).

Initially, nuclear strategy concerned only a handful of states: the United States, the Soviet Union, China, the United Kingdom, and France. These were countries embedded, initially at least, in Cold War alliances. In 1974 India tested a nuclear device; this was followed by competitive testing of weapons with Pakistan in 1998. Israel was understood to have acquired nuclear weapons during the 1970s if not earlier, and North Korea avowed its acquisition of at least one or two weapons in 2002. In 1991 it became apparent that Iraq had a vigorous and potentially successful nuclear program, and a similar Iranian program had been under way. The spread of nuclear weapons amounted effectively to a second nuclear revolution, which may have operated by a different logic than the first. The stylized (though nonetheless frightening) standoff of the Cold War was replaced by a world in which many of the same elaborate safeguards might no longer exist, by nuclear possession on the part of countries that routinely fought one another (particularly in the Asian subcontinent), and by the development of weapons small enough to be smuggled into a country in a variety of ways. By the beginning of the 21st century then, nuclear issues had revived as a subject of strategic concern, if not serious strategic thought. The proliferation of nuclear technology by a Pakistani scientist, Abdul Qadeer Khan, and the development of nuclear weapons by Kim Jong Il’s North Korea shook optimistic assumptions about the ability of the interstate system to stop marginal actors from acquiring and spreading the wherewithal to make nuclear weapons—including the possibility of terrorist groups acquiring such weapons. The overt entry of India and Pakistan into the nuclear club, the generally acknowledged Israeli nuclear arsenal, and the looming Iranian nuclear threat were no less unsettling.

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Arms control

Not surprisingly, in view of the threat of nuclear devastation, the second challenge to the traditional paradigm of strategy came from the effort to control nuclear weapons. Arms control has had a long history, perhaps as old as organized warfare itself, but it became a major feature of international politics in the interval between the two World Wars and even more so during the Cold War. A variety of agreements—from the Washington Naval Conference (1921–22) to the Anti-Ballistic Missile Treaty (1972)—constrained military hardware and forces in a variety of ways.

The theory of arms control, articulated primarily by academics, repudiated much of the logic of strategy. Traditionally, arms control has had three purposes: reducing the risks of war, preparing for the burdens of war, and controlling damages should it break out. Underlying arms control, however, lay a deeper belief that weapons in and of themselves increase the probability of armed conflict. Where Clausewitz had believed that the logic of war lay outside the realm of the forces used to wage it, arms control rests implicitly on the idea that weapons and the organizations built around them can themselves lead to conflict. Instead of war having its origins chiefly in the political intercourse of states, arms control advocates believe that war has an autonomous logic, though one that can be broken or interrupted by international agreements.

The first nuclear era, from the late 1940s through the 1990s, which was dominated by the nuclear standoff between the Soviet Union and the United States, seemed propitious for this view of the world. This was particularly true in the last quarter of the 20th century, when arms control agreements became the dominant feature of U.S.-Soviet relations and a general measure, in many parts of the world, of the prospects for peace.

The end of the Cold War meant the weakening or irrelevance of some arms control agreements, such as those that limited the distribution of conventional forces in Europe. Others were abrogated or ignored by their signatories—most notably, when the United States invoked a clause in the Anti-Ballistic Missile Treaty on December 13, 2001, to withdraw from the agreement. Other conventions remained intact, though, and seemed in some cases to assume added urgency. In particular, efforts to ban chemical and biological weapons assumed new vigour, although it was not clear whether advances in science at the beginning of the 21st century would make it impossible to restrict the development of lethal toxins or artificial plagues.

The 1968 Treaty on the Non-proliferation of Nuclear Weapons (NPT) had a mixed record in blocking states from acquiring atomic or thermonuclear weapons. The NPT, coupled with energetic diplomacy by the United States and other great powers, prompted a wide range of governments, including Argentina, Australia, Sweden, and Taiwan, to terminate or put into dormancy nuclear programs. On the other hand, at least one NPT signatory, Iraq, blatantly violated the treaty with an extremely active nuclear weapons program, which was thwarted in 1981 by an Israeli preemptive attack on the nuclear reactor under construction at Osirak and thwarted again, at least for a time, by an intrusive system of United Nations inspections following the Persian Gulf War (1991).

Still, other countries have joined the nuclear club. The open acquisition of nuclear weapons by India and Pakistan (neither of which had ratified the treaty) did not diminish the prestige or importance of those countries—quite the reverse in some ways. A determined effort by North Korea to acquire nuclear weapons, even at the expense of its previous agreements with other powers, suggested that the notion of preventing proliferation by treaty or international consensus had weakened. When, in 2002, the United States formally announced a willingness to employ force preemptively against threats to its national security, more than one observer supposed this had something to do with nuclear proliferation.

The arms control critique of strategy has its greatest force in the nuclear realm because nuclear weapons are different. Even so, the logic of Clausewitzian strategy survives. Offense exists, of course, but so too does defense, in the form of antiballistic missiles, preemptive attack, and various forms of civil defense. States acquire weapons of mass destruction for reasons that are largely political in nature. Furthermore, international agreements remain at the mercy of states’ willingness to subject themselves to them. Below a certain threshold of violence, moreover, traditional strategy still operates, as in the sparring between India and Pakistan over Kashmir. India and Pakistan, however, are states with well-developed institutions and without the urge to annihilate one another. Whether a nonstate actor, such as Hezbollah (a militia and political party in Lebanon) or al-Qaeda, would be subject to the same restraint is more questionable.