Over a quarter of a million Israelis in the south are subjected to a daily rain of Kassam and GRAD rockets. Some Jewish towns around the Gaza Strip have suffered over 4,000 rocket attacks in the past seven years. No state can tolerate a situation where a large part of its population is being terrorized by continuous rocket and mortar fire. The first obligation of any state is to provide security to its citizens. Therefore, Israeli military operations in Gaza are an imperative designed to prevent the launching of rockets into Israeli population centers and are clearly an act of self-defense sanctioned by international law. It is important to note that the Palestinians have continued their terrorist attacks in recent years despite the complete Israel withdrawal from Gaza in 2005. Instead of seizing he opportunity to engage in state-building and in improving the standard of living for Gazans, the Palestinians acted upon their hatred and continued to attack Israeli civilians, which is in itself a war crime. In contrast, Israeli military activities have never targeted civilians. Civilians are hurt occasionally in urban warfare, particularly when Hamas cynically places missile launchers or weapons stockpiles in the heart of a civilian area. These sites are, nevertheless, lawful military objectives. Under the Geneva Conventions, the responsibility for civilian casualties arising from the "shielding" lies with the party that deliberately placed civilians at risk. Moreover, Israeli military units do their best to minimize the collateral damage when attacking military targets in the midst of civilian concentrations. The officers in the field are so instructed and they have great leeway even to abort missions in case the lives of too many civilians are at stake. More than once, IDF officers have risked their own troops to prevent Palestinian civilian casualties. Israel follows strict legal standards for military procedures. Legal authorities are invariably consulted before the approval of military operational plans and all military actions are subject to stringent judicial review by the Israeli High Court of Justice - an institution with impeccable credentials. THE OFTEN-AIRED charge of disproportionate use of force by the Israeli military betrays ignorance of international law or plain desire for Israel-bashing. The proportionality of the damage done in course of military action is measured in relation to the goal to be achieved by the use of force. The legitimate amount of force for the removal of the rocket threat from a quarter of a million of Israelis is the true test of proportionality. Causing the death of any number of armed Hamas terrorists is obviously a proportionate course of action. Even hundreds of Gazan civilians hurt in a defensive battle as collateral damage are worth the lives of hundreds of thousands of Israeli civilians. Moreover, the civilians in Gaza cannot claim immunity to the consequences of the war that their leadership is conducting against Israel. Hamas was popularly elected in 2006 and every public opinion poll continues to indicate substantial support by Gazans for Hamas, as well as for terrorist attacks on Israel. Unfortunately, killing Jews is popular among the Palestinians. WE SHOULD not forget that the essence of war is a competition of inflicting pain in order to change patterns of behavior. Actually, pain may have a positive value in affecting the learning curve of the warring sides. Exacting a high cost from Hamas and the Palestinians may lead them to more peaceful behavior. It is true that it is difficult to influence the learning process of large collectives, but this has occurred before. For example, it took a lot of suffering in World War I and World War II to transform German society into becoming less militaristic and less belligerent. While advocating such an approach is not politically correct, it might be the recipe for turning the Palestinians into peaceful neighbors. Unless Hamas stops harassing Israeli civilians, Gaza and Israel are on a course of armed conflict. Israel owes its citizens relative security and it is only a question of time when Israeli troops will take over large parts of Gaza and apply the same type of treatment the West Bank received in March-April 2002. A large-scale Israeli military operation to destroy the Hamas terrorist infrastructure is inevitable. The world should be prepared for the cynical use of civilians by Hamas and the subsequent casualties. The moral responsibility for these losses clearly falls on the Islamists of Hamas. A military operation will in all probability not bring about a durable solution, however, it will drastically limit the harm Hamas can cause to Israel in the short term. If such an operation is not enough to affect the learning curve of the Gazans, additional operations are likely. Unfortunately, this is the destiny that terrorists have marked out for themselves. The writer is professor of political studies at Bar-Ilan University and the director of the Begin-Sadat (BESA) Center for Strategic Studies.