Deterrence Fails When an Enemy Thinks You Will Not Pay the Price

Here is the whole theory of deterrence in one line of arithmetic: capability times credibility equals deterrence. If either factor is zero, the product is zero. A nation with the strongest military on earth and no one who believes it will use it deters nothing. A nation with a fiercely believed will and no means to act is a bluff waiting to be called.

Most of the public argument about defense is an argument about the first number. How many ships, how many warheads, how many divisions. That is the part you can count, and it is the part that fits on a chart. The more dangerous number is the second one, because it lives in the mind of the person across the table and nobody can audit it. History says that wars begin when it drops.

Defining the terms

Let me be precise, because sloppy words make sloppy policy.

• Deterrence is persuading an adversary not to act by convincing him that the cost will exceed the benefit.
• Capability is the physical means to impose that cost: forces, weapons, bases, industrial depth.
• Credibility is the adversary's belief that you will use the capability if he crosses the line. It is a belief held by someone else, formed from your words, your past conduct, your domestic politics and your visible preparations.
• Compellence is the related task of making an adversary do something, not merely refrain. It is harder, and it is not the subject here.

One important point follows from these definitions. Deterrence is judged in the adversary's head. It does not matter what you intend. It matters what he thinks you intend. A leader who is sincerely willing to defend an ally, but who has said or done things that suggest otherwise, has deterred nothing.

The argument in four premises

1. Wars of aggression are begun by leaders who calculate that the gain exceeds the cost.
2. That calculation includes a guess about how the target and its friends will respond.
3. The guess is shaped by what the adversary has seen of your will, not only by what he has counted of your weapons.
4. Therefore, when a power's will is doubted, whether by its words, its retreats or its internal divisions, aggression becomes more likely, and the way to prevent war is to remove the doubt before the attack, not after.

That is a conservative argument in the old sense: it says the world is not made safe by good intentions, and that the surest way to keep the peace is to be visibly unwilling to lose it. Now let me show it in the record, with three cases that run from the beginning of the Cold War to its end.

Case one: Acheson and the perimeter, January 1950

On January 12, 1950, Secretary of State Dean Acheson spoke at the National Press Club in Washington. He described the American "defensive perimeter" in the Pacific as running from the Aleutians to Japan and then to the Ryukyus and the Philippines. Korea was not named as inside it. Neither was Taiwan. Beyond the perimeter, he said, the security of other areas would rest first on the people attacked, and then on the commitments of the whole civilized world under the United Nations Charter.

On June 25, 1950, North Korea invaded the South.

I want to be careful, because careful is how you earn the right to be blunt. Historians do not agree that Acheson's speech caused the invasion. The archives opened after the Cold War show that Kim Il Sung pressed Stalin for approval over many months, that Stalin's consent turned on his reading of Soviet and Chinese interests and of American readiness, and that the Soviet atomic test of 1949 and the Communist victory in China had already changed the picture. A fair reader will say that the speech was one input among several, and that it is a mistake to blame a single sentence.

But the stronger point survives that caution. The United States had withdrawn its combat troops from South Korea in 1949. It had cut its conventional forces sharply after 1945. Its public statements, from the Secretary of State on down, described a line that left the peninsula outside the guarantee. A communist leader weighing the cost of an invasion had every reason to think the cost would be low. He was wrong, and the war that followed cost more than 36,000 American lives, a figure no one planning the invasion expected to pay in return. Deterrence failed because the second term, credibility, had been allowed to fall toward zero while the first, American power, was still enormous.

Case two: HMS Endurance and the Falklands, 1982

In 1981 the British government of Margaret Thatcher, in a defense review led by Secretary of State for Defence John Nott, announced a plan to save money by scrapping HMS Endurance, an Antarctic patrol ship that was Britain's regular naval presence near the islands. Argentina's ruling junta had a long-standing claim to the Falkland Islands and was watching.

The Endurance was no match for an invasion fleet, and Foreign Office officials urged against the decision for that reason. Its value was symbolic. It said, by being there, that Britain still cared about the islands. When Britain announced it would be withdrawn, and when other signals of reduced interest followed, the junta drew a conclusion that turned out to be wrong: that Britain would not fight. Argentina invaded on April 2, 1982. The British task force sailed within days and recovered the islands by June, at the cost of 255 British lives and roughly 650 Argentine ones.

The Franks Committee, which reviewed the origins of the war, cleared the government of blame for the invasion itself, and I will not claim more than the committee did. But its report is a standing example of the principle. A cheap gesture of withdrawal, taken for sound budget reasons, changed what the adversary believed. The capability that mattered, a small ship, was trivial. The credibility it carried was not. Foreign Secretary Lord Carrington resigned when the invasion came, in acknowledgment of the failure.

The lesson cuts against the lazy view that small things do not matter. In deterrence, small things are often the signal. A tripwire is cheap. Removing it is expensive. Governments that save money by removing one tend to discover the exchange rate later, in a currency other than pounds or dollars.

Case three: Saddam Hussein reads America, 1990

In July 1990 Iraq massed troops on the Kuwaiti border after accusing Kuwait of economic offenses against it. On July 25, the American ambassador, April Glaspie, met Saddam Hussein in Baghdad. Her reported words, which were later much debated, conveyed that the United States had no opinion on Arab-Arab border disputes, while also expressing concern about the troop buildup and urging a peaceful settlement. The State Department had also told Baghdad that the United States had no special defense or security commitments to Kuwait.

Whether Saddam read the meeting correctly is a matter of dispute. Glaspie's defenders point out that she also warned him that the United States would defend its vital interests. But the problem is bigger than one conversation. Saddam had a record to read. He had seen American forces withdrawn from Lebanon after the 1983 barracks bombing, as told in Beirut 1983 Was the First Lesson in How Iran Fights Through Proxies, and he had watched the post-Vietnam debates about casualties. A leader who believes the other side will not accept body bags may reasonably conclude that he can seize a neighbor and dare the world to undo it.

Iraq invaded Kuwait on August 2, 1990. The response was not what he had assumed. President George H. W. Bush assembled a coalition, Congress authorized force in January 1991, and Operation Desert Storm expelled the Iraqi army within weeks. The record shows that the mistake was not in the capability, which the United States possessed in abundance. It was in the belief that America would not use it. And the cost of that mistake, to Iraq and to the region, was far larger than the cost of a clearer signal would have been in July.

The pattern

Put the three cases side by side and the structure repeats.

1. A large power has the capability to defend a place or an ally.
2. Through words, withdrawals or budget choices, it sends a mixed signal about whether it will.
3. An adversary reads the signal, discounts the capability, and acts.
4. The power then pays a much larger price to reverse the outcome than it would have paid to prevent it.

You cannot prove from three cases that this is a law of nature. But you can say that it is a pattern consistent with the logic, and that the opposite pattern, in which clear commitments backed by visible forces held the peace for decades, is just as striking. The North Atlantic Treaty, with American troops stationed in Europe, kept the Soviet Union from testing the line in Germany for forty years. The 1950 policy review known as NSC-68, told in NSC-68 and the 1950 Memo That Told America the Price of Staying Free, was written because the authors understood that the price of staying free had to be visibly affordable. And Reagan's military buildup of the 1980s, whatever you think of its cost, changed what Moscow believed it could win. The arms race ended not in war but in Moscow's acknowledgment that it could not keep up.

Measuring this against the founding

It is easy to treat deterrence as a Cold War technicality. It is older than that. The Preamble to the Constitution lists among its purposes "to provide for the common defence," and the Framers gave Congress the power to raise armies and to provide and maintain a navy, in Article I, Section 8. They did so because they had seen what a weak confederation invited. The new Navy of the 1790s, which began with the building of frigates in response to Barbary corsairs, was a deterrent. Washington's own advice in his Farewell Address, which people quote as if it were a pacifist's creed, said that by keeping ourselves, in his words, "on a respectable defensive posture, we may safely trust to temporary alliances for extraordinary emergencies." The text is worth reading in full, as in What Washington's Farewell Address Really Said About Foreign Entanglements. The Founders believed in readiness because they believed in peace.

The steelman: deterrence provokes arms races

The strongest objection is not a silly one. It runs as follows. When one nation builds up forces to deter, its rival sees the buildup as a threat and builds up in return. Each side's defensive measures look offensive to the other. The result is a spiral of rising tension in which both sides are less safe than before. Scholars call it the security dilemma, and the theory has examples behind it, including the naval race between Britain and Germany before 1914 and some of the worst years of the Cold War. On this view, the way to peace is restraint, reassurance and arms control, and a posture of strength becomes the cause of the conflict it claims to prevent.

I think that objection is serious, and I think it fails, for four reasons.

1. It assumes both sides want only security. The spiral model works when each state is a status-quo power afraid of the other. It does not describe a leader who wants territory, as Hitler did, or as the Argentine junta and Saddam did. Against an aggressor, reassurance reads as an invitation. The 1930s are the standard exhibit: British and French restraint did not buy peace, and the adversary treated each concession as evidence of weakness.
2. The record of weakness is worse than the record of strength. Count the cases in which an adversary attacked a clearly defended ally with a clearly credible guarantee, and compare with the cases in which a gap in the guarantee appeared. The pattern, as the three cases above show, favors the guarantee. The Cold War's big powers never fought each other directly, and the commitments that held the line in Europe were backed by forces on the ground.
3. Arms control and deterrence are not enemies. The best agreements, such as the INF Treaty, came when the American side held strong cards, as discussed in The INF Treaty Proved Arms Control Works Only When You Hold Cards. Restraint works best when it is reciprocal and verified, and the leverage for it comes from strength.
4. The cost of the spiral can be managed. The answer to a security dilemma is communication and transparency alongside strength, not unilateral weakness. A nation can announce its purposes, maintain channels to its rivals and still keep the capability.

So the objection teaches a real lesson, that signals can be misread, but it does not support the conclusion. If a buildup can be misread as a threat, a drawdown can be misread as an invitation, and history says the second misreading kills more people.

What this asks of a free country

The argument has practical implications, and they are not all comfortable for conservatives either.

• Credibility is a domestic matter. A democracy's will is read in its politics. A public that treats every commitment as a bargaining chip, or a Congress that cannot pass a defense budget on time, is signaling something to people who read newspapers for a living. The adversary studies our debates.
• Capability has to be real. Words cost nothing and everyone knows it. The production lines, the stockpiles, the repair capacity and the trained people are what make the words credible, which is why an argument about shipyards and munitions is an argument about peace. See The Defense Production Act of 1950 Is a Wartime Tool with Peacetime Habits.
• Clarity beats ambiguity when the cost of misreading is war. There are cases where ambiguity helps. Where an adversary is likely to miscalculate, it hurts. A line that is drawn clearly and defended consistently is a kindness to everyone, including the person on the other side of it.
• Discipline about commitments cuts both ways. A nation that threatens what it will not do is training its adversaries to ignore it, like a parent who counts to ten and never reaches eleven. Credibility is a bank account, and every bluff called is a withdrawal.

Why this matters at the kitchen table

A deterred war is a war that never gets a headline. That is the cruel economy of the subject: the successes are invisible. No one marks the day on which a general decided not to invade, and no one gives a medal to a budget line that kept the peace. A family in a quiet town will never be told that its son did not die in a war nobody started. But that is exactly what the investment buys, and a country that forgets this will keep learning it from the other direction, at far higher prices, as Korea, the Falklands and Kuwait each did.

The case in brief

1. Deterrence is capability multiplied by credibility, and a zero in either factor produces a zero.
2. Acheson's January 1950 perimeter speech, Britain's planned withdrawal of HMS Endurance before April 1982, and the mixed signals before Iraq's invasion of Kuwait in August 1990 show how doubt about the second factor invites attack, even though historians rightly caution that none of them was the sole cause.
3. The pattern is that a large power with ample means sends a mixed signal, an aggressor discounts it, and the cost of reversing the result dwarfs the cost of preventing it.
4. The arms-race objection describes status-quo powers well and aggressors poorly, and its remedy of reassurance has a poor record against leaders who want something.
5. A free country has to supply both factors: real forces, and a politics that lets the world see it means what it says.

What you can do: read the text of the North Atlantic Treaty, which takes ten minutes, and then ask your representative through the my-representatives page how he or she votes on funding for the readiness that makes such a pledge believable.