If a cease-fire is holding in Gaza, Hamas must be restocking;-).
Israel is in a no-win situation... literally, as I pointed out over in a Connexions thread earlier in the week. Winning against Hamas, which has Jew-hating in its DNA, means either wiping them off the map or having Hamas become willing to coexist with Israel. The later would be genocidal and the former would require a major miracle.
So, Israel can't win in a narrow sense. That makes conventional Just War applications hard to do, since you can't wipe out an idea.
Israel's strategy seems to be to root out Hamas tunnels and other key military sites in Gaza. Sadly, Hamas stashes those sites in residential areas and under schools and hospitals, so they will have plenty of civilian casualties to show the world press. That makes Israel look to be the heavy, since more Gazans will die than Israelis, causing Israel to flunk the proportionality test that JW devotees will bring to bear.
Were Israel to act proportionally, only killing as many Gazans as they lose from Hamas, it won't do much to diminish their foe's capabilities and thus make the exercise futile. Doing nothing would be the only thing that would leave Israel blameless to its non-Islamist critics (committing collective suicide would be needed to make the Islamists happy), and only a certifiably saintly leader would be so peace-loving to let his people get bombed without doing anything in reply.
Bibi ain't Gandhi. Nor would any plausible Israeli center-left coalition be turning the other cheek to that level.