The Syrian leader’s protectors send forces to support his regime in the areas it still controls.

The involvement of Iranian and Russian troops in Syria’s civil war suggests that the country’s dictator, Bashar Assad, is hunkering down in the Alawite-populated west of the country.

Reuters reported on Wednesday that Russian troops had begun participating in Syrian military operations. The report came from Lebanese sources.

American officials said Russia recently sent two tank landing ships and additional cargo aircraft to what is its only Middle Eastern client state. It also deployed a small number of naval infantry forces.

The following day, Reuters reported that hundreds of Iranian troops had arrived in Syria as well to join the forces loyal to Assad.

Fighting side by side with Syria’s regular army forces are militants from Lebanon’s Hezbollah, a group that is considered a terrorist organization in Israel and the West but is backed by Iran.

A source suggested to Reuters that the Iranian and Russian reinforcements could be deployed in the vicinity of Hama, where rebels remain active, and Idlib.

Idlib Province fell into the hands of a rebel coalition last month that is supported by Qatar and Turkey.

Among the groups now controlling Idlib is the Nusra Front, Al Qaeda’s Syrian affiliate.

The self-declared Islamic State, the most fanatical Islamist group operating in Syria, holds territory further east. It battles both Assad and the other opposition groups although clashes between Islamic State militants and the Syrian army are rare.

Last week, The New York Times reported that the rebels in Idlib had struck a deal with Assad’s allies to allow Shia Muslims from the region to flee to regime-held territory while Sunni fighters and their families would be evacuated from Zabadani, a hill station on the Lebanese border that has been under attack from loyalists.

But on Wednesday, Russian jets attacked rebels on the western edge of Idlib, casting doubt on such a truce.

The province borders on the Nusayriyah Mountains which separate the coastal heartland of Assad’s Alawite tribe from the rest of Syria.

Russia’s forces are stationed in the same coastal enclave.

If the Iranian and Russian troops deploy to defend the Alawite homeland, it would give credence to the theory — as reported by the Atlantic Sentinel as early as 2012 — that Assad’s fallback strategy is to retreat into those parts of the country that are populated by Alawites, Christians and Druze, leaving the Sunni-majority center and east to what is now the Islamic State and the northeast to the Kurds.

Such a rump state would run from Latakia in the north via Hama and Homs to Damascus in the south.

Assad has admitted that his army faces a manpower shortage and needed to give up some areas in order to defend others of greater significance.

Fred Kaplan argues at Slate that Iran’s and Russia’s interest is less in propping up Assad per se and rather to ensure they will retain their influence in Syria whatever happens to his government. If there is a transition, he writes, it will be Moscow and Tehran — Assad’s only outside protectors — that manage it. They have the most at stake.

Syria represents Russia’s only toehold in the Middle East and Iran’s gateway to interests further westward in the region (especially Hezbollah).

Both consider the Islamic State a threat only insofar it threatens their interests in the region.