Iraq’s current situation is subject to international standards and US commitments that prevent it from formally interacting with such a call. But this is not the only reason; the Syrian regime is quite condescending toward the Iraqi government, which it believes to be part of a US political process and had been pitting against it since 2003.

In addition, Assad’s call was not addressed to the Iraqi president or prime minister, but rather directly to the PMU leadership, and such a call cannot be conceived through official channels because it would be rejected.

Syria has never made an official call like that before. For instance, Hezbollah’s intervention in Syria did not follow a call; the party believed the battle in Syria to be its own and took part either as a personal initiative or in response to an Iranian command.

Calls for the PMU to intervene in Syria are not new, as many PMU spokesmen had previously mentioned this possibility when the operations to liberate Mosul first started in October. Now, however, the Syrian regime itself — and its direct leadership in particular — has called on the PMU’s intervention, which means that the sectarian war in the Middle East is entering a new phase.

BAGHDAD — On Nov. 10, the Popular Mobilization Units (PMU) announced they blocked the road between Mosul and Raqqa, thus cutting the supply lines between the cities claimed by the Islamic State (IS) as its capitals. Days later, on Nov. 16, Hadi al-Amiri , a prominent PMU leader and the head of the Badr Organization, said that Syrian President Bashar al-Assad had called on the PMU to enter Syria after liberating the Iraqi territories.

Syria resorted to nonofficial or semiofficial parties, believing that it could achieve what it had achieved during the Lebanese civil war. Syria’s Baath Party is still incapable of dealing with countries at war through their official circles, but it can easily communicate with nonofficial or semiofficial parties.

The Syrian regime’s message today is that it will be dealing with a specific counteragent to the Islamic State (IS). By calling on a Shiite militia that has achieved real victories against IS and that is larger and more powerful than Hezbollah, the regime is sending an internal message meant to stir up fear among Sunnis.

Yet on the other hand, this call seems to illustrate Syrian support of the PMU factions that want to intervene in Syria, while other PMU factions refuse to. Some PMU factions, and particularly those affiliated with Ayatollah Ali al-Sistani, are still rather conservative because Sistani refuses to fight a war outside of Iraq and has explicitly forbidden Shiite fighters from traveling to Syria since the beginning of the Syrian crisis. In addition, the Iraqi street itself does not support a war outside of Iraq.

Meanwhile, Amiri’s statement regarding Assad’s call could be an attempt to test the waters at the popular and governmental levels.

In this context, PMU security spokesman Youssef al-Kalabi told Al-Monitor, “The PMU will not make any move without the approval of the armed forces’ general commander [Prime Minister Haider al-Abadi],” noting that the PMU could be combing the borders for some “IS members,” but he did not rule out the possibility of entering into Syria “if Iraq’s national security is compromised and should the Iraqi government approve such action.”

Some PMU factions have entered Syria in the past, but once the majority of factions or the PMU’s entire strong army including its many militias and factions enter the Syrian territories, the battle for the Middle East could definitely be on the verge of a new phase.

In 2012, the Abu al-Fadl al-Abbas Brigade had announced forming its first troops in Syria to defend “the Shiite holy shrines,” although the subsequent battles they fought alongside the Syrian regime were far from the shrines. However, the momentum gained by these brigades subsided after the fall of Mosul. The bulk of those troops withdrew from Syria to Iraq after IS took over Mosul on June 9, 2014, according to some websites affiliated with the Syrian opposition. However, Hezbollah al-Nujaba, an Iraqi Shiite militia organization that adopted a slogan similar to that of the Lebanese Hezbollah, soon replaced the withdrawn troops of Abu al-Fadl al-Abbas.

Shortly after the fall of Mosul, the PMU’s fight alongside the Syrian regime entered its second phase, since the Iraqis’ intervention in Syria was no longer to defend the Shiite shrines but to fight terrorism. The fight against IS had become an international and Iraqi demand, although the battles were not only against IS, but also included anti-regime groups.

Hezbollah al-Nujaba has published several videos on YouTube of its troops in training and in combat operations in more than one place in Aleppo, including a video of its fighters on an operation south of the city in November 2015. These operations were clearly larger than those carried out by the Abu al-Fadl al-Abbas Brigade, which focused on defensive operations around the holy shrines.

Then came Assad's call, marking the third phase of the Iraqi intervention in Syria, dubbed as a comprehensive intervention by the PMU and a strengthening of the strategic Shiite alliance. This way, the presence of the armed Shiite groups would directly be under the umbrella of the Syrian regime, rather than under the management of Hezbollah or Iran.

However, should such an action take place, it would result in additional conflicts in the region and have major repercussions on Iraq, while the raging war will continue even if the Iraqi forces succeeded in liberating all territories from IS. It is also likely for this to weaken the PMU instead of strengthening it, by making its fighters intervene in battles outside of Iraq and compromise its unity since many Sistani-affiliated factions would object to the PMU’s intervention in Syria.