EVER SINCE its start six years ago, the United States has been waging the War on Terror chiefly on the Sunni side of the religious divide within Islam. The principal targets have been Al-Qaeda and its affiliates. As recently as September 2006, the White House's counter-terrorism strategy was still focused overwhelmingly on the Bin Laden network and its offshoots, which were seen as the vanguard of "a transnational movement of extremist organizations, networks, and individuals" threatening the United States.

By contrast, the vision articulated by the president in his 2007 State of the Union Address is substantially broader. It encompasses not only Sunni extremists, but their Shi‘a counterparts as well. And, for the first time, it clearly and unambiguously identifies not just "terrorism" but a specific state sponsor-the Islamic Republic of Iran-as a threat to U.S. interests and objectives in the greater Middle East.

So far, however, this shift is still more rhetoric than reality. "Our strategy to combat terrorism is really only a strategy to combat Al-Qaeda", Congressman Jim Saxton (R-NJ) pointed out in these pages not long ago. "We are not prepared to deal-in the event hostilities occur-with terrorist organizations that are built differently, like Hizballah."

Examples of this disconnect abound. The Bush Administration's original September 2002 National Security Strategy (NSS) refers generically and without distinction to the threat posed by "global terrorism." The updated version of the NSS, released by the White House last spring, does nothing to correct this deficiency. Likewise, the Bush Administration's National Strategy to Combat Weapons of Mass Destruction warns that "terrorist groups are seeking to acquire WMD with the stated purpose of killing large numbers of our people and those of friends and allies", but fails to identify whether some groups may be closer to this goal-or more capable of achieving it-than others. The National Military Strategy of the United States of America issued by the Joint Chiefs of Staff in 2004, meanwhile, simply commits the U.S. military to the generic task of confronting "terrorist forces, terrorist collaborators and those governments harboring terrorists", leaving U.S. troops to draw their own distinctions among the foes that they are fighting.

These ambiguous mission statements poorly serve soldiers in the field, who require clarity when defining their enemy-a crucial element to forming any effective strategy. They also disadvantage America's diplomats, many of whom are locked in acrimonious turf battles with allied nations about the exact scope of the War on Terror. By lumping together insurgents and guerillas, Sunnis and Shi‘a, and state and non-state actors under the generic moniker of "terrorist forces", the United States has put itself at a disadvantage in differentiating, and adapting to, enemies that are anything but homogeneous.

SIX YEARS into the War on Terror, there is considerable debate over the nature of the threat posed by Al-Qaeda. Some say that the organization has devolved from a unitary, cohesive organization into a loose movement of affiliated groups and that its ideology has undergone a similar diffusion.¹ Others believe the opposite, that Al-Qaeda is actually growing in popularity, as its brutal tactics in Iraq and Afghanistan win it sympathizers-and recruits-among idle jihadists and allow it to reconnect with fellow travelers from Chechnya to Southeast Asia.² Whatever the actual state of the Bin Laden network, one thing is clear: The disparate groups that make up today's Sunni Islamist movement tend to operate autonomously. Those countries or entities that support these radicals generally serve as enablers, rather than managers; they cannot hope to dictate the terms of the jihad waged against the West, only to sustain it and try to mold it to suit their political purposes. In turn, although organizations such as Al-Qaeda may indeed benefit from the largesse of these sponsors, they do not appear to feel lasting allegiance to them.

Yes, Al-Qaeda may receive funds and support from segments of Saudi society; officially, however, it is an enemy of the Saudi state and the central target of the kingdom's counter-terrorism efforts. In fact, no government in the world explicitly backs Al-Qaeda or extends its full protection to radical Sunni militants. Even where an intimate connection between Sunni groups and state sponsors does exist (as in the case of Syria and Hamas, or of Pakistan and various Kashmiri separatists), this support tends to be limited, carried out away from the public eye and more often than not with plausible deniability.

Shi‘a groups, by contrast, have a more direct-and durable-connection to their chief sponsor: the Islamic Republic of Iran. As Sheikh Naim Qassem, the deputy head of Lebanon's terrorist powerhouse, Hizballah, told an Iranian television channel back in April, his organization "is committed to receiv[ing] religious instruction regarding the nature of the confrontation with Israel from al-wali al-faqih", Iranian Supreme Leader Ali Khamenei himself. This direction, Qassem made clear, extends to providing sanction for the types of tactics employed by the Shi‘a militia. A similar connection can be found in Iraq, where two of the country's largest Shi‘a political parties-Islamic Call and the Supreme Islamic Council in Iraq-boast deep historic and ideological ties to Tehran, and where Shi‘a militias such as the Badr Corps and firebrand cleric Moqtada Sadr's Mahdi Army rely heavily on the Islamic Republic for financial aid, operational support and political protection.

So successful has this model proven to be that it has even attracted some Sunni radicals. These "honorary Shi‘a" include the anti-Israel Palestinian Islamic Jihad militia, which traces its ideology back to the teachings of the Islamic Revolution and sees itself as "one of the many fruits on our leader Khomeini's tree." More recently, it also applies to the Hamas movement, which, once cut off from international aid following its unexpected assumption of power in the Palestinian Authority in January of 2006, has steadily relied on Iranian largesse-and whose recent hostile takeover of the Gaza Strip was made possible in large part through Tehran's active assistance and support.

This structure bears little resemblance to the patchwork of dispersed Sunni jihadists now operating in the Middle East who, lacking explicit state linkages, are forced to obtain funds and arms through black-market operations and donations from wealthy sympathizers. Rather, the broad network of economic, political and ideological bonds that Iran has managed to form with the region's most extreme elements compares more favorably with the model of interlocking support and dependence favored by the Soviet Union in its day. In a very real sense, Iran can be said to be building a latter-day Comintern-a radical collective every bit as potent and dangerous as the one fielded by the ussr during the Cold War.

THE IMPLICATIONS of this disparity cannot be overstated. Consider a scenario in which a terrorist group seeks to obtain WMD. The working thesis is that Al-Qaeda is the group most likely to do so-by either buying weapons from weak former Soviet states or seizing them if the Pakistani state collapses. After all, Bin Laden's network is known to have sought nuclear and radiological material in the "post-Soviet space", worked to develop a rudimentary chemical weapons capability and experimented with biological agents such as ricin. It is no wonder that counter-terrorism experts believe a WMD attack by Sunni terrorists to be simply a matter of time. Nevertheless, at least for now, the difficulties of autonomously developing such a capability, or of acquiring WMD and related technologies on the open market, coupled with robust U.S. and international counter-terrorism efforts, have helped to ensure that Al-Qaeda's attempts have remained just that.

By contrast, the direct links between the Iranian regime and its (mostly) Shi‘a proxies make such a transfer more likely and more imminent. Iran's feared clerical army, the Pasdaran, serves as the custodian of the Islamic Republic's chemical, biological and nuclear programs, as well as the regime's growing arsenal of ballistic and cruise missiles. It also operates as the chief point of contact with a bevy of terrorist proxies-underlining the Iranian regime's capacity to proliferate such technologies. Iran's leaders, moreover, already appear to be moving in that direction; during the month-long war between Israel and Hizballah in Lebanon last summer, for example, an Israeli warship was hit and disabled by an Iranian variant of the C-802 Silkworm-a sophisticated missile that Israeli officials previously had not known Hizballah possessed. As this incident suggests, Iran possesses both the capacity and willingness to become an "onward proliferant" of advanced weapons.

The two groups are divided on yet another critical front: the role of the nation-state, which Sunni militants have long regarded as a "Western innovation." In contrast to their Shi‘a counterparts, militant Sunni groups tend to reject the idea of representative governance completely. Indeed, those which have chosen to govern, or been forced to do so, have come under fire from their fellow radicals. Thus, the unexpected victory of the Hamas movement in the January 2006 Palestinian elections garnered a warning from Al-Qaeda ideologue Ayman al-Zawahiri, who cautioned the group "that power is not an end in itself, but simply a stage on the path of implementing sharia law."

Shi‘a groups, taking cues from Iran, try to straddle that divide. So Hizballah now operates as a full-fledged political party in Lebanon, with more than 10 percent of the seats in the country's 128-member parliament. In the country's south, it is also much more: a virtual state-within-a-state responsible for education, health care and social services. Iran's most powerful Shi‘a allies in Iraq-the Supreme Islamic Iraqi Council and the Mahdi Army-likewise have chosen to participate in the country's nascent post-Ba‘athi government. In their choices, these groups have been deeply influenced by the example of Iran's successful Islamic Revolution.

This political involvement, in turn, provides Tehran with significant leverage over those societies-influence that the Iranian leadership can use to eliminate ideological adversaries and shape political outcomes. The extent of this authority can be seen today in Lebanon, where Hizballah, with Iran's blessing, is engaged in a slow-motion coup against the pro-Western government of Prime Minister Fouad Siniora. In Iraq too, the presence of Iranian proxies in the halls of power has allowed the Islamic Republic to exert considerable influence over the country's political direction, much to the detriment of the U.S.-led coalition.

FOR WASHINGTON, these differences should matter a great deal. They suggest that-far from the consolidated terrorist threat envisioned in current national-security doctrine-Sunni and Shi‘a groups have very different objectives and vary in their ability to attain them.

Iran is key to this distinction. Its proxies boast the official backing of a wealthy, nearly nuclear patron. Iran's support is financial; U.S. officials now estimate that Tehran "has a nine-digit line item in its budget for support to terrorist organizations." It is also operational, from a deepening Iranian strategic footprint in the Palestinian territories to the provision of arms and training to thousands of Shi‘a in Iraq. Perhaps most significant, however, is the military bulwark that the Iranian regime can offer to its terrorist affiliates against external aggression. A glimpse of this potential was on display back in 2004 when, as part of the deepening strategic ties between their two countries, Iran formally committed to defending Syria in the event of hostilities-a commitment that the Islamic Republic subsequently extended to Lebanon and Hizballah as well. Given Iran's very public atomic advances, this strategic umbrella could soon be nuclear, providing Iranian affiliates far greater freedom of action than ever before.

But this connection can also be a point of weakness. If the Sunni jihadist front can today be characterized by alignment on general ideological principles among like-minded groups, its Shi‘a counterpart is based on a state-centric model, with nearly all of its groups tethered to Tehran in some way. As such, their threat capabilities, political position and, in some instances, their very survival hinge directly upon Iran's largesse. In many ways, this makes them less durable. It is often said that the loss of Osama bin Laden or any of his top lieutenants would do little to cripple the dispersed and decentralized Sunni Islamist movement. The same survivability does not apply to Shi‘a radicals that operate with a more traditional chain of command, and with greater reliance on their chief political and economic patron. The United States must consequently work to leverage this vulnerability, degrading and denying Tehran the ability to maintain its role as a state sponsor of terrorism in the years ahead through stepped-up interdiction of arms shipments from the Islamic Republic, as well as enhanced efforts to curtail contacts between the Pasdaran and the regime's terrorist proxies.

Most of all, however, the forgoing discussion suggests that, if the United States is truly serious about waging a wider war against terrorism, it must be prepared to confront the world's leading sponsor of it. As we are beginning to learn all too well, the costs-and the consequences-of not doing so are far too high.

Ilan Berman is the vice president for policy at the American Foreign Policy Council, and editor of Taking on Tehran: Strategies for Confronting the Islamic Republic (Rowman & Littlefield, 2007).

¹See Rohan Gunaratna, "The Post-Madrid Face of Al Qaeda", The Washington Quarterly, Vol. 27, No. 3 (2004).

²See, for example, Bruce Riedel, "Al-Qaeda Strikes Back", Foreign Affairs, Vol. 86, No. 3 (2007).