"That`s because Hamas are indestructible. Aren`t they?" - H No, because you can't destroy what you don't engage. The tactics employed by Israel during Cast Lead were clearly intended to minimize casualties even if it meant little real harm was done to Hamas. To take down the militants would have meant pushing them faster than they could withdraw and taking the casualties to accomplish that goal.
Turkish warplanes hit Kurdish PKK militant targets in northern Iraq, CNN Turk reports (Reuters)
from the article: Neither Israel nor Hamas wants another Gaza war