Hamas leader Ismail Haniyeh gestures during a tent city protest along Israel’s border with Gaza on March 30. (Mohammed Salem/Reuters)

HAVING SUFFERED repeated military defeats at the hands of Israel, the Hamas movement has adopted new tactics. Rather than launch rockets at Israeli cities or stage armed attacks through underground tunnels, the Islamist movement that rules the Gaza Strip encouraged the assembly of tens of thousands of civilians last Friday for what was billed as a peaceful march on the border. In reality, it was not peaceful: While the majority of participants waited in tents, militants from Hamas and other groups charged the border fence, heaving stones and molotov cocktails at Israeli troops, rolling burning tires at the fence, and in at least one case firing shots.

Israeli troops responded just as Hamas’s leaders must have hoped, opening fire with live ammunition. Fifteen Palestinians were killed and hundreds wounded, and three more have died since. Human rights groups have reacted by pouring criticism on the government of Benjamin Netanyahu, while the U.N. secretary general and several European governments have called for an independent investigation. In sum, Hamas succeeded in dealing Israel a moral and political blow — and the demonstrations are just beginning. Hamas says they will continue until the 70th anniversary of Israel’s independence six weeks from now.

Mr. Netanyahu’s government remains counterproductively defiant. It says 10 of the 15 killed Friday were members of Hamas’s military wing or other armed groups; Hamas acknowledges five such deaths. Officials say they could not allow the militants to destroy the fence, making way for the larger crowd to cross into Israel, since that could have produced far more bloodshed. Hard-line Defense Minister Avigdor Liberman expressed no regret, saying, “all of our troops deserve a medal.”

Israel certainly has a right to defend its border from militant attacks, or even a mass peaceful invasion. But it willingly fell into Hamas’s trap by using military forces, rather than border police skilled at dispersing rioters by nonlethal means. Though tear gas and rubber bullets were also employed, the use of live ammunition ensured a high casualty rate — which, in turn, guaranteed that human rights groups and other outside observers would blame Israel, rather than Hamas.

Hamas’s resort to civil marches rather than conventional military attacks does not represent a softening of its ideology. Its leader, Ismail Haniyeh, kicked off the “March of Return” by calling for Palestinians to reclaim every inch of Israel. Rather, Hamas is reacting to Israel’s success in blunting its previous strategy. Missile defense batteries now can destroy most of Hamas’s rockets before they hit civilian targets, and many of the tunnels the group dug underneath the border to use for offensive attacks have been detected and destroyed.

Countering Hamas’s new tactics will require a more subtle Israeli response. It should be possible to turn away attacks on the fence without shooting and killing large numbers of militants; Israeli forces have become adept at that on the West Bank. Hamas’s rule of Gaza is under considerable pressure: Egypt has sealed its border, and the rival Palestinian Authority has cut back funding. Hamas is seeking to revive itself by having Israel create new “martyrs.” The Netanyahu government should do its best not to cooperate.