At this writing, Israeli tanks are gathered outside the Gaza fence, poised for a major offensive. The prime minister is warning that no one connected to Sunday's killings of Hanan Barak and Pavel Slutsker and the capture of Gilad Shalit will be off-limits. An investigation has been set up to try and determine how it was that a primitive tunnel so easily breached the border, and how the IDF was caught unawares, despite intelligence warnings, so that lessons can be learned for the future. One easily discernible lesson is plainly that the IDF, and by presumed extension the political leadership, had not fully internalized how Israel must be deployed along a hostile border. A significant part of the rationale behind last summer's disengagement from the Gaza Strip was that it would create more defensible lines. The more efficient security deployments that were envisaged all-too evidently were not put in place here. Though the border with Gaza has long been fortified, it is far from clear that it has been reenforced as befits a line that no longer has the IDF deployed on both sides of it. The immediate challenge, however, goes beyond better fortifying ourselves against attack, whether by missiles or through tunnels. It relates to ending the attacks. Such attacks can only be prevented if the price the Palestinian leadership pays for ordering or acquiescing in them is much higher than any conceivable benefit. The price to be exacted must necessarily combine military and non-military actions by Israel, preferably supported and supplemented by sanctions imposed by the international community. Israel should stress to foreign governments that such a combination of Israeli and international action would, by far, be most effective at preventing further Palestinian attacks and eliminating the necessity for further Israeli defensive measures. But if necessary, Israel must be prepared singlehandedly to raise the price of attacking us to prohibitive levels - even if the Quartet is not helpful, and even if it is partially working at cross purposes. It is said that a massive military operation in Gaza, along the lines of the Defensive Shield operation in the West Bank in 2002, would accomplish little because the infrastructure of terrorism would be rebuilt once Israel pulls out. It could also be argued that if the PA came under massive international pressure then Israeli military action would likely be unnecessary, because the Palestinians themselves would quickly end their attacks and take concrete actions to prevent terrorism. Finally, we cannot ignore the risk to our own soldiers from such a difficult operation. Such concerns are not trivial. In reality, however, both diplomatic and military action are necessary and should be mutually reenforcing. Furthermore, it is not true that military actions against terrorism have no effect. It is no coincidence that a Hamas spokesman quickly and in Hebrew called on Israel not to "escalate" after its own attack against Israel. Hamas knows that Israel can deal a serious setback to the terrorist infrastructure that it has been building rather than dismantling, and that Israeli military action will mean that Hamas has delivered the opposite of the improved situation for Palestinians that it promised in the elections that brought it to power. In recent weeks Israel, encouraged by the international community, has been stressing that it is waiting, and hoping, for the Palestinian leadership to radically change its behavior and facilitate a new effort at negotiation. Negotiations between Fatah and Hamas over the "prisoner's document" have to some extent obscured the fact that even if Hamas were to agree to that formula, it will not have fulfilled any of the three conditions imposed by the Quartet for resuming direct assistance: ending terrorism, accepting previous agreements, and recognizing Israel's right to exist. Yet though the financial pressure on Hamas has been substantial, Hamas evidently still believes that the Quartet will back down on its principles before Hamas must, and that its own electoral success and Israel's withdrawal from Gaza have granted it a substantial degree of immunity from Israeli military action. Israel cannot become reconciled to a war of attrition with the Palestinians; the Palestinian attacks must end. And this can only be done by substantially raising the price of Palestinian aggression through diplomatic, economic, and military means.