Syrian armed forces hollowed out by low pay and corruption folded easily to a rebel advance after Iranian forces and militias backed by Tehran pulled out following Israeli airstrikes, Reuters reported citing Syrian military and militia sources.
The shock exit of President Bashar al-Assad from the country his family has ruled for half a century deprived Iran of one of its oldest and most stalwart allies.
Damascus was a key bridge in a so-called Shi'ite crescent which projected Iran's influence over Iraq and Syria to its armed Lebanese allies Hezbollah.
Iranian, Hezbollah and Iraqi militia forces had been a key bulwark for Assad in his fight against armed rebels which spectacularly faltered in a shock offensive which seized the capital on Sunday after less than a fortnight.
Those foreign units were Assad's top asset, Reuters cited the regional sources as saying, and Iranian military advisors and the militias ran the operational command structure that defended the Syrian state.
Many of the Iranian advisers quit Syria following Israeli air strikes on the capital in the spring and the rest left as the insurgent thrust gained steam last week, Reuters reported citing Iraqi militia commanders.
A source familiar with Hezbollah thinking was cited as saying fighters from the group had mostly left the country in October to confront an Israeli air and ground assault at home.
Alone, the Syrian military lacked a coherent strategy to defend their lines especially around the northwestern city of Aleppo - the country's second largest - which fell rapidly to radical Islamist-led rebels with little fighting.
US sanctions, mismanagement and corruption had taken its toll on the Syrian economy and military for years, undermining morale and willingness to fight.
Many rank-and-file soldiers and officers simply discarded their uniforms and weapons as opposition fighters made gains and melted into the civilian population.
For years before the government's ouster on Wednesday, monitoring groups reported that the Syrian military had been reduced to a militia-style organization focused on repression and was less prepared for a conventional military campaign.
