This week, the Islamic State destroyed Mosul's most sacred mosque: The Great Mosque of al-Nuri.

Think about that carefully.

The Islamic State, which claims to be the ordained servant of God on Earth, blew up one its God's holiest houses.

That tells you everything you need to know about these terrorists.

Still, while all mosques are sacred within Islam, the al-Nuri mosque was special. Constructed in the 12th century, its age and unique architecture stood as a marker for Mosul. The Sunni mosque endured Mongol invasions, the feuds of the Ottoman Empire, the and World Wars I and II, Saddam Hussein's brutality, and the 2003-2009 chaos of al Qaeda in Iraq.

It stood for nearly 850 years. Until this week.

As Iraqi counterterrorism units approached the mosque, Islamic State fighters appear to have detonated explosives. The Islamic State denies responsibility for the destruction, but both the U.S. and Iraqi forces have placed the blame on the terrorists.

They are right to do so.

After all, the Islamic State has long waged war on holy sites. As I've explained, the group's propaganda thrives on the desecration of Shiite mosques and other holy sites. And all across the world, Islamic State fighters have targeted churches, museums and other testaments to diverse faith and knowledge. The Islamic State believes that individual freedom to think, worship and love are atrocities.

Like the Nazis, Islamic State fanaticism has no boundaries. Just as Hitler let Berlin burn rather than surrender to inevitability, the Islamic State chose to destroy this mosque rather than cede it to more honorable Muslims.

The terrorists must be confronted for this crime against humanity and Sunni Islam. The Iraqi government should work expediently to provide proof of Islamic State responsibility. Doing so would unveil the terrorists for their true nature. The Islamic State cloaks itself in a narrative of Islamic service. But their annihilation of a Sunni mosque speaks to a different reality.

The Islamic State is a death cult. And its master, Abu Bakr al-Baghdadi, is the defining Islamic apostate.

In July 2014, al-Baghdadi preached from the al-Nuri mosque in celebration of the holy month of Ramadan. "It is a month", he said, "that begins with mercy, continues with atonement, and concludes with salvation from the hellfire."

Three years later, as this year's Ramadan comes to an end, al-Baghdadi's hypocrisy has never been more obvious.

His mercy is measured only in murder. His need for atonement is unparalleled. And the hellfire, whether from a predator drone or from God, will eventually consume him.