The following is why Israel will keep up with the air strikes even though major Hamas headquarters are gone.

A top Hamas leader and several members of his family were killed Thursday in an Israeli air strike in the Gaza Strip, as Israel pressed its offensive for a sixth day and a Hamas rocket destroyed part of an apartment building in the Israeli port city of Ashdod.

Nizar Rayyan, a cleric who served as a liaison between Hamas's political and military wings, had called for renewed suicide bombings inside Israel and refused to go into hiding, as other prominent Hamas members had done. His death, confirmed in a statement issued by Hamas, marked the first known killing of a senior leader of the militant group since Israel began air strikes on Saturday. Two of Rayyan's four wives and four of his 12 children were also killed after Israeli forces bombed their apartment building, Palestinian health officials said.