An Islamic gunman walks past a pick up truck belonging to the "Raqa Regional Public Service" headed by the Islamic State (IS) group loaded with the wreckage of a Syrian government forces aircraft which was shot down by IS' militants over the Syrian town of Raqa on September 16, 2014. The plane crashed into a house in the Euphrates Valley city, the sole provincial capital entirely out of Syrian government control, causing deaths and injuries on the ground, Syrian Observatory for Human Rights monitoring group said.AFP/Getty Images

This article is from the archive of our partner National Journal

Over its history, the United States has only rarely faced a foreign threat that persisted for a generation or longer. Conflict with Great Britain flared for roughly four decades after the Revolutionary War. The Cold War with the Soviet Union lasted nearly 45 years.

An Islamic gunman walks past a pickup truck belonging to the "Raqa Regional Public Service," which is headed by the Islamic State, loaded with the wreckage of a Syrian government forces aircraft. (STR/AFP/Getty Images)All evidence indicates that the struggle against radical Islamic extremism is destined to join this short list of prolonged challenges. The fact that the Islamic State coalesced so quickly after al-Qaida weakened suggests the rise of radical groups is driven as much by demand as supply: So long as there is a critical mass of recruits sympathetic to jihadist ideology, an organization will emerge to mobilize them. If we destroy ISIS, something resembling it will probably resurface sooner rather than later—absent an improbable transformation of attitudes among the radicalized minority in the Muslim world.

Yet nearly 14 years after the 9/11 attacks, America's political leadership remains far from agreement on a sustainable strategy for engaging with this conflict. The contrast with the Cold War is telling. Despite differences in emphasis, this far into the Cold War, both U.S. political parties had largely accepted the overriding strategy of containment. Today, the parties are split over how to respond to Islamic radicalism, and even over what to call it. Nothing better illustrated this divide than the gaping partisan fissure over Israeli Prime Minister Benjamin Netanyahu's speech to Congress on Tuesday, denouncing President Obama's ongoing nuclear negotiations with Iran.

America is bitterly divided over the threat of Islamic extremism partly because we are now bitterly divided over almost everything. But the impasse also reflects disappointment with the initial responses by presidents from each party.

George W. Bush's domestic antiterrorism architecture has largely survived, with some reassessments by Obama. But the disillusioning results in Afghanistan and Iraq discredited Bush's vision of a "global war on terror" powered by U.S. military force. Obama understandably recoiled from those failures. But even some Democratic thinkers believe he has overcorrected, both by downplaying the depth of the radical threat and by overly limiting America's role in responding to it. "Obama has been imprisoned by the Iraq and Afghanistan experience," maintains Will Marshall, president of the Progressive Policy Institute, a centrist Democratic group. "You have to pick your fights carefully "¦ but just staying out of a conflict is no guarantee that you're going to escape worse consequences." Critics like Marshall believe that the United States has been forced to pursue greater military intervention against ISIS now partly because it failed to support a moderate Syrian opposition earlier.

The disappointment with both presidents shows how delicate the dance can be between intervention and restraint—particularly in a generational struggle that unfolds across many fronts, in ever-evolving forms. In evaluating those difficult choices, the best compass is to seek in our strategy what Cold War thinkers called "solvency": a sustainable balance between the nation's ends and means.

It's against the yardstick of solvency that Netanyahu's speech most conspicuously failed. The prime minister identified admirable goals: dismantling Iran's uranium-enrichment capacity and transforming its regime. But he offered no plausible means to achieve them. He suggested that tough sanctions coupled with the threat of force would eventually cause Iran to buckle. But sanctions alone haven't stopped other nations from pursuing the bomb—or halted Iran's own advances. Even air strikes would only delay Tehran's efforts. Besides, there is little American appetite for any military intervention in Iran "while we have our hands full against ISIS," Marshall notes.

Even with stringent verification requirements, any achievable nuclear agreement would contain and defer rather than eliminate the Iranian nuclear threat. There's risk in reaching such a deal. But the evidence suggests there is greater risk in failing to do so. The administration's best argument is that opponents like Netanyahu have not offered any achievable alternative that could stall Iran's nuclear program for nearly as long as the 10 years or more Obama is seeking in an agreement. While Netanyahu wouldn't say so, the sweeping goals he identified likely could be achieved only by a full-scale military invasion that deposes the Iranian regime.

In a generational conflict, avoiding the wrong battles (Vietnam, Iraq) becomes as important as winning the battles we join. If negotiations fail, the risk of sharper conflict with Iran, which could eventually demand air strikes, would escalate. But the principle of solvency argues for taking every reasonable step to avoid fighting a cold war (much less a hot one) against the region's leading Shia power while facing a metastasizing threat from Sunni radicals.

Allowing Iran to remain a nuclear-threshold state increases its influence and could magnify tensions across the region. But an agreement could also strengthen the forces inside Iranian society that believe their country would benefit from greater engagement with the West. And bending Iran's trajectory even slightly away from confrontation and toward integration would pay compounding dividends during a struggle with radical Islam that will likely test America for decades.

This article is from the archive of our partner National Journal.

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