Reports indicate that Iran and Hezbollah are "building a network of militias inside Syria to protect their interests" should Syrian President Bashar al-Assad capitulate or have his government overrun.
The militias are currently fighting side-by-side with Assad's forces--trying to ensure the Syrian government stands. However, a senior Obama official says both Iran and Hezbollah are working to be sure they have reliable forces in place to do what needs to be done should Assad fail.
Currently, Iran is sending weapons and cash to fighters in Jaysh al-Sha'bi, "a force supervised by Iranian and Hezbollah commanders."
These Jaysh fighters serve as proxies for Iranian forces and Hezbollah fighters.
Reports also indicate the Iran expects Hezbollah to serve them well if Assad's regime collapses. In particular, Hezbollah will be expected to keep a supply route into Lebanon open so munitions and other war materials can be transported as needed.