In 1976, Israel gave in to demands of the "Popular Front for the Liberation of Palestine" and agreed to release dozens of terrorists. In exchange for the release of 106 hostages it held in Entebbe, Uganda.
The ultimate question of loss versus gain is the one that should be asked even today, when we come to discuss a possible deal with Hamas. If the concession does not harm the further crushing of Hamas and the occupation of the entire Gaza Strip, then the concession in itself will be dwarfed in comparison to the human blow.