In many international conflicts some of the greatest potential for escalation and hindrance to de-escalation come not from the main parties to the conflict but from the fringe—from extremist groups that have no desire to be part of a plausible peaceful order and aim to spoil any progress toward establishing one. In Northern Ireland, for example, much of the slowness in moving toward a peace agreement even after the main IRA had decided to accept one was due to continued terrorist operations by die-hard groups that had splintered from the IRA. In South Asia, the pace of Indian-Pakistani detente has been set too often by terrorist groups rather than by the two governments. In the various dimensions of the conflict between Israelis and Arabs there also have been numerous instances of the extremist fringes of both sides exacerbating tension and impeding any lessening of it.

The attack Sunday in the northeast corner of the Sinai peninsula falls into the same mold. Armed gunmen overpowered an Egyptian border post and then used stolen Egyptian vehicles to race across the Israeli border before being stopped by Israeli airstrikes. The attack, by as yet unnamed militants in the Sinai, was against the interests of all of the major players in the area, and all of those players condemned it. Egypt had 16 of its soldiers killed as well as control of its sovereign territory challenged. Israel was the target of an armed assault across its border, even if a small one. For Hamas, the ruler of the Gaza Strip, the attack suspended a hoped-for expansion of its commerce with Egypt. One of the Egyptian responses to the incident was to close indefinitely the border crossing at Rafah, which has been almost the only point of significant relief from the Israeli blockade and isolation of Gaza.

One of the ways in which fringe-perpetrated incidents increase tensions among major players is by stimulating false accusations of responsibility. The incident in the Sinai is no exception. Statements from both the Egyptian Muslim Brotherhood and Hamas suggested that it was somehow an Israeli operation. Meanwhile, the Israeli ambassador in Washington, perhaps operating on general instructions to blame Iran for anything it can possibly be blamed for, declared on Twitter and his Facebook page that “Iranian-backed terrorists” were the perpetrators. There was no more evidence for this than for Israeli involvement, and Israel's defense minister, Ehud Barak, later said the attackers were part of "apparently some kind of global jihad, with unclear connections"—which is probably the most that can be said about them so far.

The main parties to a long-running conflict should respond to an incident like this by using it as an opportunity to act on their shared interests, not to make propaganda. Egypt, Hamas and Israel all share an interest in curbing the extremists who—based not just on this incident but several others—appear to have made increasing use of the Sinai as a base of operations, especially since the beginning of the distractions and disorder in Egypt associated with the overthrow of Mubarak. Egypt and Hamas should show no tolerance for ludicrous accusations against Israel, such as that it engineered an attack that ended up being aimed at its own territory. Israel needs to do some more fundamental rethinking, especially regarding what it wants from its peace treaty with Egypt. Linked to that agreement were severe restrictions on what military forces Egypt could deploy in the eastern Sinai. Such restrictions made sense in the 1970s; they make less sense now, given a military balance that renders preposterous the idea of Egypt wanting a new war with Israel, along with internal security in this part of Egyptian territory having become a more serious concern for both countries. Israel has granted piecemeal permission to Egypt to increase its Sinai deployments somewhat beyond the limits originally established when the treaty was signed. This amounts to micromanaging how another country arranges its own military forces on its own territory. Evidently the Israelis are worried that a more wholesale revision of the deployment restrictions might cause the peace treaty itself to unravel. That would not be a problem if the other part of the Camp David accords were observed.

Israelis also need to realize that, just as even the closest allies have some conflicts of interest, even the bitterest of enemies have some shared interests. No provision for security in this corner of the Middle East can ever be complete without including whoever governs the Gaza Strip. Security problems illustrated by Sunday's incident on the border are reminders of how the policy of trying to strangle Hamas rather than dealing with it does not serve anyone's interests, including Israel's.