This Photo Is The Clearest Sign Of An Imminent Iraqi Civil War

Things look like they are about to get much worse in Iraq.

Sunni militants of the Islamic State of Iraq and Syria (ISIS) - now flush with looted cash and armed with American weapons and tanks - are pushing closer to Baghdad, and now civilians there are signing up in droves with the Shiite militias that gained notoriety during the bloodiest days of the Iraq War.

"This is the start of the Iraqi civil war that was so obviously going to break out after we washed our hands of it," The Brookings Institution's Kenneth Pollack told The Washington Post, while predicting Iraqi security forces would end up fighting alongside Shiite militiamen and the Iranians.

There has already been widespread sectarian conflict in the country for quite some time, as much of the country's Sunni minority look on Iraqi Prime Minister Nouri al-Maliki with suspicion and disdain.

But the situation has gotten more tense in recent days, as militants have seized key cities of Fallujah, Tikrit, and Mosul. With Mosul in the north ISIS scored its biggest victory, taking control of the country's second-largest city (home to roughly 2 million people).

If ISIS does attempt to strike Baghdad, "they won't be likely to seize [it]," a former senior U.S. defense official told Business Insider, while adding that the city has seen widespread purges and executions of Sunnis under Maliki. Instead of attack the city, however, they may resort to a terror campaign of car bombings and improvised explosive devices.

"I don't think [ISIS] can go into a principally Shia city and not get a bleeding ulcer where they just get tied down," a retired senior U.S. military officer said, on condition of anonymity.

Nevertheless, Shi'ites in Baghdad are mobilizing. Thousands of men have responded to a call to arms by Ayatollah Sistani, 83, who is the highest religious authority for Shi'ites in Iraq. During Friday prayer, one of his representatives read a statement pronouncing "the legal and national responsibility of whoever can hold a weapon to hold it to defend the country, the citizens and the holy sites."