Hamas supporters counter that the blockade Israel imposed on Gaza in 2007 is the equivalent of violence against civilians, since it is they who suffer. But the blockade is in fact an alternative to violence, the very kind of thing that those who object to the use of force suggest.

It is also worth noting that the blockade could not work without Egypt’s cooperation. Egypt has been critical of Hamas for renouncing the ceasefire and resuming offensive operations, and sees Gaza as a refugee crisis in the making. (In January 2008, hundreds of thousands of Palestinians flooded into Egypt, and not all returned.) Egypt also openly fears the spread of Iranian influence in the region, and Hamas is increasingly a creature of Tehran. Thus it makes strategic sense for Egypt to try to keep Hamas in a box. It will be interesting to see what the Egyptian representatives have to say at a prospective Arab summit on the crisis, if one even happens.

One gathers that these critics are relying on the principle of proportionality. While this is an established principle in just-war circles, it is a bit suspect. If all uses of force were proportional, how could one side gain a decisive advantage? Would not such conflicts drag on indefinitely, compounding the needless death and destruction? If a country is able to prevail in a conflict quickly, doesn’t that country owe it to its own people to do so? Besides, what is a proportional response to Hamas’s policy of firing rockets and mortars into populated areas? Should Israel respond in kind, killing civilians purposefully and gaining no military benefit? Those who object to Israel’s target list should be required to suggest which Hamas installations should be left standing — and why.

Also, even if proportionality is the standard, there is proportionality in objectives: Hamas seeks to destroy Israel, and Israel’s current offensive (as explained by several of the country's leading officials) is designed to destroy Hamas. If the war is back on, it makes sense for Israel to fight to win. The Hamas leadership should have considered that possibility before deciding not to renew the ceasefire.

Regarding Israel’s excessive use of force (which Gen. Sec. Ban Ki-moon, and others, have alleged), one might ask for a definition of "excessive." If the definition is "more than necessary to be effective," then Israel has actually used insufficient force, since Hamas is still launching rockets (though nowhere near the “thousands” they threatened).

And regardless of how Israel goes about fighting Hamas, the results could bring real change to the region. The Fatah faction is watching the destruction of the Hamas infrastructure in Gaza with some interest. Palestinian Authority officials have indicated they are ready to take over in Gaza should Israel “finish the job” and oust the Hamas regime. The top Hamas leaders in Gaza, Ismail Haniyeh, Mahmoud Zahar, and Said Siam, who said they would be “honored” to become martyrs for the cause when the offensive commenced, have seemingly had a change of heart and gone into hiding. Some reports say that there is a sense that the Hamas infrastructure is starting to crumble.

It is unclear whether Israel will mount a major ground offensive. It is hard to see how the gains from the air campaign can be solidified without some type of ground action. This will entail some casualties, but if anything was learned from the 2006 war against Hezbollah in Lebanon, it is that Israel must move swiftly and decisively.

The country should not enter into a ground war lightly, especially one that will involve much fighting in difficult urban areas: Halting half-measures will play into the hands of Hamas, which will attempt to replicate Hezbollah’s brand of asymmetric warfare. Moreover, the political ends of such an incursion should be kept in mind at all times. Go in if needed, hand over power to another group (if Fatah, so be it), then get out and declare victory. If it can be wrapped up before the U.S. changes governments on January 20, so much the better. Just get it done. National Review by — NRO contributor James S. Robbins is senior fellow in national security affairs at the American Foreign Policy Council, and author of Last in Their Class: Custer, Pickett and the Goats of West Point.