When waged with appropriate means to achieve realistic ends, the answer is, “It’s a really effective means of  imposing your will on the enemy”. Don’t take my word for it. Listen to senior Hamas leader Mahmoud Zahar. He classifies those who continue to fire rockets at Israel as rebels and continues:

“Did we agree to the truce [the one agreed with Israel  that brought Operation Cast Lead to an end ] in order to stick to it, or to violate it?,” Zahar said. “Do they expect us to give a round of applause to people who rebel against their organization?” he asked, referring to so-called rebels firing rockets in violation of the truce. Referring to Hamas’ stance toward the launches, Zahar said that allowing “to open the gates of defiance could lead to anarchy.”

Statements like this offer further vindication for Operation Cast Lead and show the leadership of Hamas to have a  firmer grip on reality than that of many members of the organization’s fan club among the international left.