The incident in which some 40 Palestinian civilians were killed when Israel Defense Forces mortar shells hit an UNRWA school in the Jabalya refugee camp Tuesday surprised no one who has been following events in Gaza in recent days. Senior officers admit that the IDF has been using enormous firepower.

"For us, being cautious means being aggressive," explained one. "From the minute we entered, we've acted like we're at war. That creates enormous damage on the ground ... I just hope those who have fled the area of Gaza City in which we are operating will describe the shock. Maybe someone there will sober up before it continues."

What the officer did not say explicitly was that this is deliberate policy. Following the trauma of the war in Lebanon in 2006, the army realized that heavy IDF casualties would erode public (and especially political) support for the war and limit its ability to achieve its goals. Therefore, it is using aggressive tactics to save soldiers' lives. And the cabinet took this into account when it approved the ground operation last Friday, so it has no reason to change its mind now.

Nor is it likely that Tuesday's incident, with its large number of civilian deaths, will result in an immediate cease-fire. Civilian deaths increase international pressure for a cease-fire and so the incident will probably bring the end of the war closer. Nevertheless, the Second Lebanon War continued for weeks following a similar incident at Kana.

Moreover, the situation in Gaza is slightly different than it was in Lebanon. First, until Tuesday's incident, the world appeared relatively indifferent to Palestinian civilian casualties. On Monday, 31 members of the Samouny family were killed when a shell hit their house in Gaza City; that same day, 13 members of the Al-Daiya family where killed by another Israeli bomb. Yet international media coverage of these incidents was comparatively restrained.

Second, none of the major international players want to strengthen Hamas. France and Egypt are currently leading the cease-fire efforts, yet their proposals are far closer to Israel's demands than to those of Hamas. Therefore, unless Hamas gives in and accepts these proposals, the fighting is likely to continue.

What to do about Hamas' arms smuggling currently appears to be the main sticking point holding up a cease-fire agreement. Israel is holding intensive talks with the United States in an effort to reach a deal that would be acceptable to Egypt. The proposals include sending in the U.S. Army's engineering corps to systematically destroy the entire Philadelphi Road, where the smuggling tunnels under the Gaza-Egypt border are located.

Three years ago, on the eve of the disengagement, then GOC Southern Command (and now Deputy Chief of Staff) Dan Harel proposed digging a canal the entire length of the Philadelphi Road to thwart the smuggling. At the time, his idea was dismissed as crazy. So Israel withdrew without any arrangements in place for Philadelphi, and the tunnels under the road became a smuggling superhighway for the rockets now being launched at Be'er Sheva, Ashdod and Gedera.

The delay in the diplomatic negotiations is liable to bring about a further escalation of the fighting. The cabinet will soon hit another moment of decision, when it will have to decide either to expand the operation by deploying the reservists who are now training at Tze'elim, or to accept what from its view is an imperfect cease-fire deal, followed by a rapid withdrawal. It is a classic risk versus reward assessment: Do the chances of improving the war's outcome outweigh the risk to soldiers' lives inherent in a broader offensive, or vice versa?