In Syria a key factor in the government forces ability to reverse rebel gains over the last year has been the appearance of thousands of Lebanese Hezbollah gunmen. Iran helped create Hezbollah in the 1980s and has financed the survival and growth of Hezbollah ever since. In addition to cash and weapons, Iran has provided military training. A lot of the training has been basic military stuff, but there’s been a lot of specialized instruction (terrorism, espionage, counter-espionage, planning and so on). Thus while the Hezbollah “army” only consists of about 2,000 full timers and 10,000 part timers, there is also a much larger force of trained reserves (trained personnel no longer on the payroll). Many of these reservists have been called on to “volunteer” to spend 3-6 months fighting in Syria. That has been very dangerous, with about 2,000 of the Hezbollah men serving in Syria in the last 18 months getting killed or wounded in action. Iranian cash and other resources have come in handy here because Hezbollah has been able to provide death benefits for those killed in Syria and free (and extensive) medical care for those wounded. More money is paid to Syria veterans recovering from wounds and pensions for those crippled by their wounds.
For the Syrian government, which is also subsidized by Iran, these Hezbollah military efforts have been crucial because Hezbollah’s paramilitary force is one of the most effective in the region. Over the decades Hezbollah has developed effective tactics to fight Israeli troops and hostile militias and Islamic terrorist groups in Lebanon. Israel can still beat Hezbollah fighters, but with greater effort than against other Arab irregulars. In Syria this Hezbollah experience, training and professionalism has been a nasty shock to the rebels. Hezbollah fighters can operate as effectively (and often more so) than trained Syrian soldiers, but also fall back on many terrorist and commando techniques they have learned from the Iranians and decades of combat inside Lebanon and on the Israeli border. Inside Syria the Hezbollah fighters are feared by the rebels and respected by the Syrian soldiers.