Conor Cruise O'Brien, the Irish statesman and historian, once wrote: “The best way for a democracy to deal with what is called political violence is to set aside its supposedly political character and concentrate on its criminal aspect as an armed conspiracy.” O'Brien, who died this month, had particular sympathies with the security dilemmas faced by Israel. And in Operation Cast Lead in Gaza this week, Israeli politicians are plainly adopting a similar diagnosis to his.

No democratic government should underestimate the provocations that Israel has endured from relentless shelling of its civilians. For the nearly 400 Palestinian deaths so far that have resulted from Israel's attacks this week, Hamas must accept a large share of responsibility. A comprehensive peace settlement is as far away as ever, and Israel is justified in seeking to constrain Hamas's capacity to inflict harm. But Israel's leaders would do well to consider how a political strategy might reinforce the prospects for an eventual negotiated settlement.

Israel's military campaign has so far met with some success. Khaled Mashal, Hamas's leader in exile, is reportedly willing to renew the ceasefire if Israel halts its bombardment. Israel will reasonably respond that this is scarcely a concession. The entire rationale of the Middle East peace process is to trade land for peace. Israel withdrew from Gaza in 2005. It has secured not peace, however, but a renewed campaign against its civilians. International suggestions that Israel's campaign is driven by domestic imperatives are accurate, though that is hardly surprising. Hamas's activities have themselves affected Israeli politics, by seemingly substantiating the warnings issued by Binyamin Netanyahu, the hawkish leader of Likud. The Government of Ehud Olmert is responding to the demonstrable failure of disengagement to provide for Israel's security.

Hamas's conduct has made it more difficult for Israel to plan on an early withdrawal from the West Bank. The goal for Israel in targeting Hamas is to hamper the ability of terrorist groups to operate. By doing so, Israel will be pursuing more than a narrow security imperative. Preventing Hamas's attacks should hasten withdrawal from the West Bank and enhance the prospects for the eventual creation, as justice and equity demand, of a sovereign Palestinian state.

But as they consider a 48-hour humanitarian ceasefire to allow aid to enter Gaza, Israel's leaders will be reflecting on an unenviable range of choices. If Israel persists with an aerial campaign, then the very success of its actions so far will have diminished the number of military targets and increased the risk to civilians. Israel has a right to defend itself but criticism from some European governments that disproportionate force is being used might soon become more persuasive in these circumstances. The use of ground troops would be risky, owing to the inevitable casualties that Israel would suffer. But the third option, of withdrawing after initial successes, would recall the inconclusive and politically damaging Lebanon campaign of 2006.

There are two ways in which politics might be brought to bear on this conflict. Pressure by an intermediary - possibly Egypt, or Tony Blair in his capacity as Middle East envoy - on Hamas to announce a ceasefire, and Israel to respond, is necessary. But it will be a temporary palliative, even if successful, while Hamas's rejectionist aims are unchanged. An armed conspiracy must be confronted. But - as the remarkable turn in the fortunes of Iraq this year suggests - it can also be undermined by shrewd diplomacy. Israel should reiterate willingness to move speedily to a territorial accommodation, even with a Hamas-led government, conditional on a permanent abandonment of violence.