Muslim-on-Muslim -- Arab on Arab -- bloodletting: Sunni Jihadis in Iraq Carry Out Biggest Atrocity in Recent Memory Against Shiites

In what may be the worse expression of Muslim-on-Muslim -- Arab on Arab -- bloodletting that has wracked the Middle East in recent years, Sunni extremists in Iraq say they have massacred 1,700 unarmed Shiite soldiers, The New York Times reported.  

The Islamic State in Iraq and Syria (ISIS) carried out the slaughter in Tikrit— Saddam Hussein's former base— posting photographs on its Twitter feed and warning that more killing was to come.

Saddam was Sunni ruling over a majority Shiite population.

The mass murder could unleash a wave of Shiite reprisals against Sunni civilians elsewhere in Iraq.

Twitter is now blocked in Iraq and people are largely unaware of what happened in Tikrit.

ISIS has taunted the U.S. to come to the aid of the Shiites "Soon we will face you, and we are waiting for this day," the group's leader Abu Bakr al-Baghdadi said in a statement aimed at Washington.

The Sunni jihadis captioned photos of the atrocities they committed to ridicule Shiites: "The filthy Shiites are killed in the hundreds," read one. "Look at them walking to death on their own feet," read another. A third said: "The liquidation of the Shiites who ran away from their military bases." Yet another warned: "This is the destiny of Maliki's Shiites."

Nuri Kamal al-Maliki is the Iraqi prime minister.

None of the pictures posted showed more than 60 victims in a frame and the 1,700 figure is unconfirmed.

The BBC reported that some photographs showed large numbers of Shiite men being transported "away" in trucks.

Shiite Grand Ayatollah Ali al-Sistani had previously called his followers to arms to block ISIS but instructed them to "exert the highest possible level of self-restraint" – presumably a message not to engage in the wholesale slaughter of Sunni non-combatants, according to the Times. 

The Shiite-led Iraqi security establishment has played down reports of the atrocity or denied it altogether, the Times reported. But one senior government official said, "I don't doubt they are real, but 1,700 is a big number. We are trying to control the reaction."

ISIS aims to create a Sunni caliphate across the entire Middle East in part by inflaming sectarian tensions. The group was inspired by al-Qaida but Baghdadi no longer accepts the authority of al-Qaida chief Ayman al-Zawahiri, The Daily Telegraph reported. 

Who stands in the way of ISIS? The Islamist Persian regime in Iran which espouses its own brand of Shiite extremist Island and the Arab Shiites in Iraq.

It would be a mistake to see the concurrence of interests between Tehran and Washington to stop ISIS as a channel to find common ground. 

Naturally, we can expect President Barack Obama to get this wrong.

But the US remains the Great Satan to Iran even if the ISIS is the near term threat to their hegemonic regional designs.