The rise of the Islamic State of Iraq and Syria represents a significant failure of U.S. policy. However, ISIS so far does not pose a significant security threat to America that requires military action.

Despite its successes, ISIS lacks the strength necessary to capture Iraq’s capital, let alone gain control of the majority-Shia nation. Most important, so far, is that, ISIS, unlike al-Qaida, has not confronted the U.S. Thus, Washington should react circumspectly, avoiding further unnecessary entanglements.

Recent experience offers several sobering lessons for confronting ISIS’s rise.

Intervention brings unintended, unpredictable and uncontrollable consequences. America’s experience in the Middle East highlights how one intervention almost always begets another. Removing Saddam Hussein triggered years of bloody conflict. Even if the new government in Baghdad had backed a continued U.S. military presence, the latter likely would not have prevented hostilities from exploding today. Barring reconciliation, opined Adm. Michael Mullen, chairman of the Joint Chiefs of Staff, in 2007, “no amount of troops in no amount of time will make much of a difference.”

War is rarely required against America’s potential adversaries. A restrained U.S. response emphasizing overwhelming retaliation, with allies taking principal direct responsibility for their security, is the best foreign policy approach.

In contrast, transnational terrorist groups, such as al-Qaida, are almost impossible to deter. So far, however, ISIS’s fighters act more like an irregular military. In fact, the organization’s break with al-Qaida in part reflected the latter’s focus on the “far enemy,” that is, the U.S. ISIS’s recent verbal threats against Washington appear intended to deter American involvement.

Moreover, the group will have trouble maintaining its gains. The organization’s Iraq success has depended on support of Baathist loyalists and tribal leaders, who are most interested in winning a better deal from Baghdad. Few Sunnis appear interested in returning to the 7th century.

Indeed, prior radical control — and brutal jihadist behavior — in Iraq helped spark the Sunni Awaking. Clashes between ISIS and other Sunnis already have occurred. U.S. military action almost certainly would result in more costs than benefits. Washington has learned the limits of military power, especially when imposed from afar with little public support for what amounts to international social engineering.

Inserting military advisers is risky. Many Iraqi military units likely are infiltrated by ISIS and other extremists, making U.S. personnel vulnerable to attack, rather like in Afghanistan, with the spate of “green on blue” killings. Drone strikes against ISIS’s leadership would not likely be enough to break the group.

Airpower has become the preferred military panacea. But ISIS has mixed guerilla with conventional tactics, making it a difficult target. Air strikes would have limited effectiveness in urban warfare and could not liberate captured cities. Worse, intervening militarily without separating ISIS from other Sunni groups almost inevitably would mean killing people once allied with Washington against al-Qaida as part of the “Sunni awakening.”

Washington loses by giving a blank check to Baghdad. Iraqi Prime Minister Nouri al-Maliki has misgoverned, exacerbated sectarian tensions, and weakened his nation’s governing institutions. Supporting his government would reward behavior which has helped bring his country to near ruin.

The administration long has unsuccessfully pushed al-Maliki to be more inclusive. Washington now is pushing for his ouster, but any replacement might not be much better. Moreover, unconditionally backing Baghdad risks foreclosing potential solutions, including some form of federalism or even partition.

Backing the Syrian resistance risks further undermining the Iraqi government. The civil war in Syria long has been beyond Washington’s control. Funding the opposition would help contain ISIS only if groups focused their efforts against ISIS. But that will never be their primary objective. The Damascus government is odious, but not as inimical to U.S. interests as an ISIS “caliphate.”

ISIS is more a problem for America’s friends than for America. Islamic extremism most directly threatens countries in the region. These states, overwhelmingly Muslim other than Israel and Lebanon, possess greater credibility in confronting ISIS. Iraq must convince the group’s Sunni allies to cooperate with a reformed government in Baghdad rather than reconstruct an ancient caliphate.

Turkey has a capable military. Aid from Saudi Arabia and other Gulf States to extremist opposition forces in Syria has proved counterproductive. Other countries, including Israel, Jordan and Lebanon, have an interest in rolling back ISIS’s gains.

U.S. options are limited. ISIS has grown out of past U.S. policy mistakes. Washington cannot afford to be stampeded into another unnecessary and counter- productive war.