It isn’t easy being a Sunni supremacist, least of all ISIS. Having been bombed by Turkey, Iraq, Russia, the Assadist remnant in Syria, and the United States, now the so-called Islamic State can add Iran to the list of air forces strafing the caliphate’s shrinking forces.

But this strike is different from previous anti-ISIS sorties, which the Pentagon claims happened as early as 2014. Iran’s considerable rocket and missile inventory was utilized for a bombardment of Dier ez-Zur, a city in eastern Syria, which is still partially under control of Iran’s ally, Bashar al-Assad. The city has been surrounded by ISIS forces since 2014, when Free Syrian Army fighters melted away during ISIS’s blitz across Syria and into Iraq.

The attack was in retaliation for an earlier terror assault on Iran’s parliament by ISIS fighters in Tehran, the country’s capital, on June 7, according to a statement from Iran’s hardline Revolutionary Guards, the military elite, who control much of the country’s foreign policy and military-industrial complex.

It may seem odd that Iran, which has sponsored terror attacks against both Israel and the United States, would be at loggerheads with ISIS, who also despise the West. But there have been massive changes in Iran that has shifted it away from its post-1979 revolutionary terrorism, while ISIS holds a Sunni-supremacist worldview that makes virtually every person in the world, minus their direct adherents, either enemies, subjects, or slaves.

Iran’s Shi’a Islam is considered blasphemous by ISIS, who have called for the “cleansing” of entire countries of Shi’a people. It can be hard to tell the difference between Shi’a and Sunni Muslims, but it’s not too different from Catholics and Protestants, with many core beliefs being similar, but many rituals and heroes being different. While both sects accept the Prophet Mohammed and the Qu’ran as the core of their faith, they differ as to who took over the Muslim community after his death. Over 1,300 years later, and both major sects have big enough differences that it isn’t hard for an ambitious leader to stoke conflict between them.

That’s exactly what ISIS seeks to do, attacking Shi’a in Syria, Iraq, and now Iran, in hopes of causing the Shi’a to overreact and attack Sunni communities. When that happens, Sunnis will flee into ISIS’s arms, giving them new recruits motivated to fight their long war for the Muslim world. That was the strategy of ISIS’s Iraqi predecessor, al-Qaeda in Iraq, in 2004-06, when it succeeded in sparking a civil war between Iraqi Sunnis and Shi’a.

Iran launched a mid-range ballistic missile attack in Deir-ez Zor, Syria, in retaliation for terrorist attacks in Tehran: Tasnim news agency pic.twitter.com/HMD1p33qTy — People's Daily,China (@PDChina) June 18, 2017

That last time didn’t work out so well for al-Qaeda in Iraq, however, when Iraqi Sunnis decided they’d rather ally with the Americans than with the increasingly hated al-Qaeda. Still, ISIS seems committed to trying the strategy again and again.

Iran’s rocket barrage, as opposed to a more accurate missile attack, where the projectiles might have had the ability to change course, is exactly the retaliation ISIS wants from the Islamic Republic. Depending on how many civilians were killed in the attack, ISIS’s propaganda department will almost surely blast that this Shi’a war crime against Sunnis must be avenged. The war between Iran and ISIS, in other words, is just beginning.

[Featured image by Majid/Getty Images]