Deterrence is one of the hallmark concepts of the international system. It keeps governments honest; convinces rogue (but rational) leaders to refrain from being reckless; and makes the world a more stable place by preventing a shooting war between great powers. Without deterrence, the nuclear contest between the United States and the Soviet Union could have been a whole lot worse.

Yet there are cases in history when deterrence failed to dissuade a state from invading a neighbor. In one of the most in-depth reports conducted on the topic, the RAND Corporation studied why deterrence sometimes proved ineffective and why some leaders engaged in what in hindsight appears to be irrational behavior.

One of the more interesting case studies investigated was Saddam Hussein’s August 1990 invasion and subsequent occupation of Kuwait. Why, despite facing insurmountable odds against a far more powerful and technologically sophisticated U.S. military, did Saddam decide to overrun his smaller neighbor?

1. Bush administration floundering:

A year after the Iran-Iraq War concluded in a ceasefire, U.S. policy on Iraq revolved around normalizing relations with Baghdad and assuring that American firms would have access to the Iraqi market during the country's postwar reconstruction. The George H.W. Bush administration understood that Saddam Hussein was a ruthless dictator with a history of making bad decisions, but the White House remained hopeful it could tame the dictator’s ugly streak and perhaps encourage his regime to be more predictable. The administration also thought Saddam was more interested in rebuilding his country after eight years of war with Iran rather than launching another invasion—an assumption that would turn out to be naive as soon as Iraqi tanks breached south of the Iraqi-Kuwaiti border.

2. Two-faced messaging:

According to the RAND study, “the United States did not issue clear and strong warnings to Saddam regarding the costs he would incur should he invade Kuwait.” The warnings that came from the Bush administration were confusing and at times contradictory. While the State Department reminded Saddam that the United States was deeply committed to keeping the Strait of Hormuz open to oil traffic and to defending its Persian Gulf allies, Washington also went out of its way to assure Saddam that U.S. military deployments in the region were not specifically geared towards protecting Kuwait from a possible Iraqi invasion. President Bush sent a letter to Saddam on July 28—five days before the invasion—that although the U.S. was concerned about Iraq’s posturing, Washington hoped to address these differences “in a spirit of friendship and candor.” That same day, U.S. ambassador April Glaspie stated to Saddam that the United States held no position on inter-Arab border disputes, sending an implicit message to the Iraqi dictator of American neutrality.

All of this, the study suggests, may have provided Saddam with the assurance that he could invade his smaller neighbor and get away with it—or at the very least do so without the U.S. inflicting massive retaliation. Indeed, a month into the Persian Gulf War, Secretary of State James Baker agreed with the proposition that stronger U.S. rhetoric could have stopped the invasion from happening.

3. U.S. intelligence community ignored:

In multiple reports circulated to policymakers during the Reagan and Bush administrations, intelligence community analysts assessed that Saddam often engaged in high-risk behavior and likely viewed the oil fields in Kuwait as a prime target of opportunity. Approximately a week before Iraq’s invasion, CIA intelligence officer Charles Allen predicted that the mobilization of Iraq’s forces was a prerequisite for an Iraqi offensive. The Bush administration held a different view; Baghdad wasn’t preparing for an invasion, but bluffing in order to scare Kuwait into concessions.

4. Saddam’s paranoia:

While Washington and Baghdad were transactional allies during the Iran-Iraq War, Saddam was reportedly deeply upset when the Iran-contra scandal broke. Here was the United States, a supposed partner, selling TOW missiles to his enemies in the middle of an existential conflict. The news of a U.S.-Iran backchannel during the war changed Saddam’s frame of mind about Washington’s intentions and moved him towards the conclusion of the United States as a duplicitous power. The study notes that “by 1990, Saddam may have interpreted all efforts by the Bush administration to improve relations to be empty rhetoric, and therefore analyzed all U.S. actions through his paranoid prism.”

In Saddam’s mind, the United States was a snake seeking to overthrow his regime. If Washington’s policy was regime change, Baghdad would be better served acting in Kuwait rather than being restrained; at least Saddam would possess more leverage when the inevitable arrived.

5. Saddam miscalculated America’s response:

While Saddam expected some degree of U.S. military retaliation in the event of an occupation of his Kuwaiti neighbor, he misinterpreted the lengths to which Washington would go to push his army back into Iraq. Using the Vietnam War and the 1984 withdrawal from Lebanon as evidence, officials in the Iraqi leadership described Saddam as a man who doubted the American people’s patience and will for a long, bloody military campaign. He overestimated the Iraqi army’s strength and significantly underestimated Bush’s willingness to back up his “line in the sand” commitment with a large and multinational military operation.

The Iraq-Kuwait case study is an instructive one for U.S. foreign policy officials. If Washington wants deterrence to succeed in the future, it must be absolutely clear about what the United States is willing to tolerate and what kind of behavior would result in retaliation. Just as important in the equation is a single, unified position from the entire U.S. government, as well as open-lines of communication to the potential adversary about how far the United States is willing to go if a line is crossed. If an adversary is not convinced the United States will respond, it becomes that much more likely deterrence will fail and a new war will begin.

Daniel DePetris is a fellow at Defense Priorities, a nonpartisan foreign-policy organization focused on promoting security, stability and peace.

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