The Guards run the show in Iran

In recent weeks, as Washington ratcheted up pressure to designate Iran's Islamic Revolutionary Guard Corps as a terrorist organization, officials throughout Iran sprang to its defense. The sermon by Ayatollah Ahmad Jannati last month was typical. The corps "is not separate from the people," Mr. Jannati told the congregation. "Are you introducing the 70 million people living in this country as terrorists?"

This public embrace makes devising effective sanctions against the corps problematic. Still, the United States must find a way to contain the Guards – they help run Iran's nuclear program, have a hand in killing US soldiers in Iraq, and are playing an increasingly prominent role in Iranian politics.

The corps was created shortly after the 1979 Islamic Revolution because the loyalty of the conventional armed forces was in doubt – the officers were suspected of harboring monarchist sympathies, and those who had undergone training in the US or Europe were viewed as potential foreign agents.

The result was two parallel military institutions with distinct responsibilities. The corps is responsible for protecting "the revolution and its achievements," according to Iran's constitution, whereas the conventional military is tasked with protecting the country's independence and territorial integrity.

Roughly one year after the corps's creation, Iraq's president Saddam Hussein launched a war against Iran that would last eight years and cost hundreds of thousands of lives. The early corps cadres earned public respect with their abundant courage and enthusiasm and the regime glorified their actions even more.

The corps still has the traditional responsibilities of a military force. It has roughly 120,000 men in uniform and a much larger reserve called the Basij, and its leaders boast about observing US military tactics in Afghanistan and Iraq and being ready to counter these with asymmetric warfare. The corps also has a naval branch – it captured British sailors in March – and an air force.

The corps' unconventional warfare function is performed by its Quds Force. This entity is involved with the insurgency in Iraq, and in 2002 the US accused it of fighting in Afghanistan. The corps was instrumental in the creation of Hizbullah in Lebanon in the 1980s, and its personnel were in Bosnia in the 1990s.

What has changed about the corps is its political role. It now has the characteristics of what political scientists call a praetorian force, wherein higher-ranking officers participate in political affairs, sometimes at the behest of civil authorities. Praetorians also reveal a mistrust of civilian leaders. An examination of statements by Maj. Gen. Mohammad Ali Aziz-Jafari, who was chosen as the new head of the Guards on Sept. 1, illustrates these points. In 1999, as Iranian students staged mass demonstrations, Mr. Jafari was one of 24 corps commanders who, in an open letter to President Mohammad Khatami, warned they would take matters into their own hands if he did not act.

"The corps is not just a military organization," Jafari said in 2002. "It is a politico-military organization. The corps is different from the military." He went on to explain why it was speaking out on a wider range of subjects than before. "Today, America is issuing threats and, unfortunately, there are groups that are prepared to sacrifice the main goals and principles of the revolution in pursuit of their own political aims. That is why the corps has expressed its views." He suggested that the current Supreme Leader, Ayatollah Ali Khamenei, does not have the gravitas of his predecessor, also necessitating greater activism by the corps.

Recent personnel moves suggest that the corps is being prepared to play a key role in parliamentary elections scheduled for March 2008. In August, corps officer Alireza Afshar was selected as the Interior Ministry official in charge of elections. Mr. Afshar replaced a close ally of President Mahmood Ahmadinejad, himself a former Guard, and joined former deputy corps commander Mohammad Baqer Zolqadr.

The corps also is a major player in the Iranian economy. It is connected with more than 100 business entities ranging from defense industries to smuggling. Its engineering arm – Khatam ol-Anbiyeh (Sword of the Prophet) – employs 40,000 people, and in just one month it won three contracts worth some $7 billion.

Designation of the corps as a terrorist organization would require freezing any assets it has in the US. In practical terms this is meaningless, because the corps does not have any assets here. UN Security Council Resolutions 1737 and 1747 – passed in connection with Iran's nuclear and ballistic missile programs – identify several corps officers and call for restrictions on their overseas travel and assets. This too is fairly meaningless, because corps members are unlikely to travel to the US or Europe or keep money in foreign banks. As these efforts demonstrate, and in light of the corps's decisive role in Iranian politics and its significant economic power, the ability of sanctions to restrain the organization is questionable. A combination of assertive diplomacy and robust sanctions that target the real engines of the regime – its energy sector, trade, and finance – is more likely to affect Iranian behavior.