Know them by their deeds, not words. Although the old-school leaders of al Qaeda still rage against the US and jihadists welcome any chance to harm us, look at who the terrorists actually kill. We’re not the main target of Sunni extremists these days. Iran, along with its allies, tops the list.

Of course, we cannot let down our guard and should hunt down Islamist terrorists where we can, but the focus of the “field soldiers” serving al Qaeda’s most-active franchise in Syria and Iraq is on Iran’s ambitions and Shia Muslims, not on us.

To the horror of diplomats and theorists who’ve denied the role of faith in religious terrorism, we are witnesses to a regional conflict between Sunni and Shia Muslims stretching far beyond the Syrian cockpit.

Yesterday’s suicide-bombing of the Iranian embassy in Beirut, Lebanon, amplified the breadth of this distinctly uncivil war within Islam. The Abdullah ­Azzam Brigades, a Lebanese al Qaeda franchise, claimed responsibility, citing Iran’s use of Hezbollah Shia militiamen to support the Assad regime in neighboring Syria. Wounding at least 140 victims, the attack killed 23 outright and appears, to this ­analyst, to have targeted the Iranian “cultural attaché,” who was killed while walking with a Lebanese security chief. In Iranian diplomacy, “cultural attaché” translates as “spymaster.”

Beyond the borders of nervous Lebanon, the slaughter has been under way for years, since Islamist extremists of multiple stripes hijacked Syria’s anti-Assad insurgency. Even earlier, the Sunni-Shia divide flared in Iraq as Iran moved to exert Shia ­hegemony.

Every day, with every local massacre, sectarian lines harden. In this multi-sided conflict, atop the maelstrom of the “Arab Spring,” people are killed not only for worshiping the wrong god, but for worshiping the right god in the wrong way. The unleashed hatreds are so intense that we’ve been pushed to the sidelines, still a desirable target, but far away. History’s law is that, while humans may relish hating a distant enemy, they generally prefer to kill their neighbors.

If we have been, for now, demoted to second place in the Great Satan Sweepstakes, Israel, too, has slipped down on the target list. The hate-rhetoric continues, but Hamas is basically quarantined in Gaza; the Palestinian Authority excites little active support; and external actors who had been rocketing Israel are vigorously butchering fellow Muslims.

Of course, the age-old Persian-vs.-Arab rivalry, power politics, local issues and even personal grudges complicate the spreading strife, but only a career diplomat could be so naïve as to deny that this, at bottom, is a contest between Islam’s two major branches. And there is nothing we can do to resolve it. We can only play on the margins — and we do so at our peril.

But crises sometimes offer opportunities. When Western and Iranian diplomats meet again this week to discuss the existential (certainly, for Israel) issue of Iran’s nuclear ambitions, our delegation should do the strategic math — which adds up to a desperate Iran.

To date, we’ve got it backward with the domestically reeling Obama administration frantic to sign a treaty it can claim as a success (you want it bad, you get ­it bad).

Sanctions on Iran are biting deep. That’s why Iran is willing to talk at all. But we need to grasp that Iran’s also struggling to maintain its sphere of influence in Syria and Lebanon, and sanctions play into that, too. Iran’s stretched thin, its economy grievously wounded.

We, not the mullahs, hold the winning hand. We would be foolish, indeed, were we to give the Iranians sanctions relief for empty promises.

Our diplomats obsess on obsolete borders and fail to connect a bombing in Beirut, the carnage in Syria and Iran’s pursuit of nukes with an overarching and gruesome sectarian struggle. Doing so would make Washington uncomfortable.

But thanks to the carnage in the Middle East and the sanctions regime, we’re in the strongest position vis-à-vis Iran since the fall of the shah. And in this perverse world, al Qaeda helped. Strike while the car-bomb’s hot.

Ralph Peters is Fox News’ strategic analyst and a retired Army intelligence officer.