Israel Dropping Northern Bridges - Signaling A Broader War? (Poll)

 Israeli aircraft blasted main roadways north of Beirut for the first time in the three-week conflict on Friday, knocking out four key bridges.   This seems to signal a shift in strategy as the IAF struck key infrastructure in Lebanon's christian heartland.

Okay, this makes no sense unless Israel wants to isolate southern Lebanon even more than it is now.  Why?   I don't know but there are more than one possible explainations.

Israel has shown from day one that they are pursuing a prepared stategy.  This sometimes appears like two thugs duking it out in knee-jerk fashion but both sides appear to have been planning this war for years.   We can assume that Hezbollah will keep fighting until there is nothing left to fight with so lets look at the Israelis.  What do you think Israel's strategy is?  Keep in mind, I want the thinking of the Israeli war cabinet, not the mensh on the street.