Dabq, the English language magazine published by Islamic State, devotes its most recent issue to the cause of killing Shia Muslims. 

Contained in its 56 pages is the theological justification for the wholesale slaughter of Shia men, women and children.

Fox News:

The 13^th issue of Dabiq, a copy of which was provided to FoxNews.com by the Middle East Media Research Institute (MEMRI), is titled "The Rafidah: From Ibn Saba' To the Dajjal." Rafidah is derogatory term for Shia Muslims that translates to “rejecters.”

In the forward of the issue, the terror group praises the Dec. 2 terror attack in San Bernadino, Calif., calling it a demonstration of Muslims’ willingness to make sacrifice for the sake of “fulfilling their duty to Allah.” The forward then uses the attaclks carried out by married couple Syed Rizwan Farook and Tashfeen Malik as a call to arms for targeting "crusaders" on their own soil.

“The spark has been lit here in Iraq, and its heat will continue to intensify – by Allah’s permission – until it burns the Crusader armies in Dﾄ｜iq,” reads a quote from Abu Mus’ab az-Zarqawi, an Iraq-based Al Qaeda leader killed in 2006.

The issue also touches upon other matters, including an article on the recently killed executioner for ISIS, “Jihadi John,” an article praising the widows of ISIS fighters and a piece blasting Saudi Arabia.

But what is most clear throughout the issue is a concerted effort to wipe out the Shia population of the Middle East. At first glance, it may seem odd that ISIS is focusing its efforts against fellow Muslims and not the West, but Mauro says that it is part of a very elaborate campaign on the Islamic State’s part.

"It is still important for ISIL to attack the U.S. and Europe for branding purposes," Mauro said. "It helps them make their case that they are looked favorably upon by Allah and that they are growing stronger, regardless of whatever territorial losses they suffer on the ground.”

Recently, it was discovered that Islamic State is cutting the salaries of their fighters in half. Along with this shift in emphasis to killing fellow Muslims, is this a sign that ISIS is weakening?

ISIS territorial losses have been significant but hasn't changed the strategic calculus of the US in going after them. They've been shown to be incapable of holding on to captured territory when pressed by trained soldiers. But they have also shown a capacity to absorb the kind of bombing being carried out by Russia and the US.

And they have yet to make a concerted effort to hold what they captured. The victory by Iraqi troops in Ramadi came because the Iraq government committed 10,000 troops against just a couple of hundred ISIS fighters. Most of them escaped to fight another day. The coming offensive to retake Mosul, a city of a million people, will tell us a lot about what ISIS is prepared to do to hold their most significant conquest in Iraq.