Our parents are our greatest teachers. One of the earliest - and most important - pieces of wisdom I ever received from my father was his admonition to me that "anything worth doing is worth doing well - and to the end." The debate now rages on within the inner circles of power as to whether we should wrap up the war in Gaza, pull out and accept a cease-fire, or carry on until the Hamas threat has been sufficiently neutralized, if not destroyed. Oddly enough, there seems to be a surprising role-reversal at work. Defense Minister Ehud Barak, a decorated general we would expect would want to keep on fighting, is arguing for a halt to the campaign, while Prime Minister Ehud Olmert, whose conversion to a dove has seen him argue strenuously for a Palestinian state, wants to keep the attack going. No one can say that this operation was a rash and impetuous descent into danger. Olmert's first words on the war stated that Israel had tried every means possible to prevent an invasion, and that, finally, we had exhausted all the peaceful avenues to rein in Hamas and prevent our cities from being daily target practice for their deadly ordnance. But now that casualties - and world pressure - are mounting, and fear of a second - or third - front is growing, there is a real fear that we will close out the Gaza war before having achieved our objectives. And that would be a tragic mistake, almost as severe as the disengagement and premature end of the Second Lebanon War. WAR IS hell - always has been, always will be. Lives are disrupted, suffering abounds, the best and brightest of our young people are put in harm's way and may - God help us - make the ultimate sacrifice. The worst peace, it can certainly be argued, is preferable to the best war. Yet there are times when war is justified, inevitable and even righteous. Combating a cruel enemy who is sworn to our destruction and armed to the teeth, and who is making our daily life unlivable, adds up to a conflict from which we cannot run away, but must see through to its conclusion. History can also be a great teacher. Let us go back, for a moment, to the spring and summer of 1945. Germany has surrendered on May 7, ending the war in Europe. After six years of the bloodiest fighting the world has ever known, peace is on the horizon. But Japan has vowed to fight on against the allies, swearing eternal loyalty to Emperor Hirohito and launching numerous suicide kamikaze attacks on American and British targets. And so, on August 6, president Harry Truman makes the momentous decision that the new atomic bomb - mankind's most frightful weapon of mass destruction - should be used against the Japanese. The nuclear attack on Hiroshima kills 70,000 people in the initial blast, with double that number eventually succumbing to their wounds. But the bloodletting is not over; three days later a second nuclear device is detonated over Nagasaki, killing another 40,000 Japanese civilians. One week later, on August 15, 1945, the Japanese unconditionally surrender, and the global community sighs in relief as World War II finally comes to an end. At university, I once asked my history professor why it was necessary to drop that second atomic bomb. Would the Japanese not have been sufficiently horrified by the effects of the Hiroshima blast to sue for peace and lay down their weapons? His answer was terse, but telling: "When you are fighting for your lives against a fanatical enemy, you don't take chances; you finish the job." DESPITE WHAT you may see in the world media, and the rhetoric of our adversaries, we Jews are a merciful, compassionate people. We have a doctrine of "purity of arms" unparalleled among the world's militaries. Our soldiers are paradigms of morality and grace under fire, and we avoid civilian casualties whenever and wherever we can, often at great risk to our fighters. We have absolutely nothing to be ashamed of vis-a-vis our conduct on the battlefield. But there comes a time when forbearance and mercy are no longer a virtue. When dealing with an enemy that seeks our extermination and denies our very right to exist, we have no obligation to hold back. Indeed, we have no right to ease up, knowing that our civilian population will pay a heavy price for every moment of weakness that we show. Daily recesses are fine for kindergarten and high-school classes, but they have no place in a struggle for safety and survival. Instead, we have to gather up our courage, resist the urge to compromise and pull the proverbial trigger on this mission. We may have entered this war hesitatingly, with trepidation and with great reluctance, but now that we're in it, we must finish the job. The writer is director of the Jewish Outreach Center of Ra'anana; his son Ari fell in battle against Hamas terrorists in 2002.