Nearly three months have passed since the Russian offensive in Syria began Sept. 30. The Russian intervention first targeted rebel strongholds in northern Syria and is now focusing on the Sheikh Maskin area in the south. Experts say the Free Syrian Army took the brunt of the onslaught.

According to a recent report by the Institute for the Study of War, Russia's involvement in the Syrian civil war has shifted the battlefield momentum in favor of President Bashar al-Assad. It reads, “In Aleppo province, the Islamic Revolutionary Guard Corps and associated proxy forces launched a multipronged offensive on Oct. 15 that has seized large swaths of rebel-held terrain in the southern countryside of Aleppo City.” According to the same report, pro-regime forces achieved tactical gains against the opposition in northeastern Latakia province. The FSA is currently present in northern Syria around Aleppo and Hama as well as in southern Syria.

The FSA is considered the biggest and most secular of the rebel groups currently fighting the Assad government. Its estimated 35,000 fighters are mostly defectors from the Syrian military, according to Syrian analyst Sinan Hatahet from the Istanbul-based think tank Omran Dirasat.

In an interview with Al-Monitor, Hatahet explained that the organization consists of about 27 larger factions, each comprised of an average of 1,000 fighters as well as some smaller units or localized militias, some as small as a few dozen militants. There are thousands of brigades of various sizes.