SO FAR Hamas’s military campaign against Israel has been a dismal failure. Thanks in part to Israel’s Iron Dome anti-missile system, some 1,200 rockets fired at Tel Aviv, Jerusalem and other cities have caused only one Israeli death and a few other casualties. Attempted commando attacks via the sea and a tunnel were stopped short, and a drone that ventured into Israel was quickly shot down. Yet Hamas on Tuesday rejected an Egyptian cease-fire proposal that was supported by Western governments and the Arab League and had been accepted by Israel.

Why would Hamas insist on continuing the fight when it is faring so poorly? The only plausible answer is stomach-turning: The Islamic movement calculates that it can win the concessions it has yet to obtain from Israel and Egypt not by striking Israel but by perpetuating the killing of its own people in Israeli counterattacks. More than 200 people, including a number of children, have already died in Gaza; Hamas probably calculates that more deaths will prompt Western governments to pressure Israel to grant Hamas’s demands.

So far, the tactic is not working. Secretary of State John F. Kerry on Tuesday condemned Hamas for rejecting the cease-fire and “us[ing] the innocent lives of civilians . . . as shields.” But Hamas’s commanders, who have burrowed into underground bunkers, appear to be doubling down. They are urging civilians who have left their homes to return, including some 15,000 who evacuated the northern part of Gaza in response to Israeli warnings. The cease-fire proposal was answered with a new barrage of missiles aimed at central Israel.

To be sure, the Israeli government of Benjamin Netanyahu has more incentive than Hamas to agree to a cease-fire, even though a majority of the Israeli public probably opposes it. Israel has little to gain from a prolonged conflict; a threatened ground invasion of Gaza would cause heavy casualties on both sides and, if it destroyed Hamas, leave Israel with the problem of finding a new government for the territory. Mr. Netanyahu is seeking the renewal of the truce that ended the last Israel-Hamas mini-war, in 2012. That would end attacks on both sides while allowing for a gradual opening of Gaza’s border for civilian trade.

Hamas’s rejection reflects its weakened position compared with two years ago. Egypt’s military government has shut down most of the cross-border tunnels that Hamas depended on for weapons as well as revenue, making it impossible for the Gaza administration to pay its workforce. The Islamists sought relief by forming a unity government with the secular, West Bank-based Fatah movement, but that did not lead to the payment of salaries or the reopening of the border with Egypt. Following the kidnapping and murder of three Israeli teenagers last month, Israel arrested dozens of Hamas’s operatives in the West Bank, making their release another objective of the missile attacks.

Mourners gather at a funeral at a mosque in Rafah, southern Gaza Strip. (Lefteris Pitarakis/AP)

To its credit, Israel has used sophisticated technology, including targeted text messages and dummy warning missiles, to minimize civilian casualties. But innocent people will inevitably be killed in attacks on launchers and missile factories that are purposely placed in densely populated areas. The right response of the international community is not to surrender to Hamas’s despicable tactics but to continue insisting that it unconditionally accept the cease-fire proposed by Egypt.