By sending ground troops into the Gaza Strip, Israel has crossed a line that brings it perilously close to strategic failure.

Just as with the Lebanon war of 2006, an air bombardment has failed to stop rocket fire into Israel - and has been followed by a ground invasion. The Israeli government says it has learnt the lessons of its stalemated war with Hizbollah, the Lebanese militia. Gaza is more hospitable terrain than southern Lebanon; Hamas is militarily weaker than Hizbollah; Israel is better prepared and is using new tactics.