The debate as to what constitutes a just war is ancient. The old saying “all is fair in love and war” might be true for love, but it is patently untrue for war. Politicians, diplomats, scholars, theologians and lawyers have devoted a great deal of their time to the challenging task of establishing criteria for waging a just war.There is no justification for war except for aggression. Aggression justifies two kinds of violent response: Defensive war by the attacked party, and a war of law enforcement by the attacked party and by any other nation of the international community. The justice of war, “jus ad bellum,” concerns the reasons that brought about the war; ideas about righteous reason, righteous authority, righteous intention. The justice of the cause needs to be sufficiently great to warrant warfare.While war should be the last resort and peace is always desired, still, sometimes war is an ugly necessity in order to avoid an even greater evil.More than 100,000 people have been killed in Syria since the civil war there began. President Barack Obama’s foreign policy goal is to bring American troops home, reduce military intervention in the world, and secure US borders. This policy is contrary to that of Obama’s predecessor George W. Bush, who had no qualms about sending American troops to wage war in Iraq and a futile war in Afghanistan. Obama is reluctant to interfere in conflict zones.Thus he has observed the killing in Syria and opted for limited American involvement – supplying the Syrian opposition with weapons. Obama is also unsure who would replace Assad. Hence it was possible for the Syrian civil war to take its toll for so many months.However, the use of chemical weapons is beyond the scope of tolerance. Observing the criteria of just war, waging war on Syria, after a long period of probing and after exhausting other alternatives, seems inescapable.Without a decisive action against the Assad regime we can expect a continuation of bloodshed.Tens of thousands more would be killed and the region would remain volatile and unstable.Now it is time for Obama to assert leadership as president of the only superpower, as the leader of the free world.IT WOULD have been sensible to exert pressure via the United Nations. The forerunner of the United Nations, the League of Nations, was established in 1919 under the Treaty of Versailles “to promote international cooperation and to achieve peace and security.”At the conclusion of WWII, in 1945, representatives of 50 countries met in San Francisco at the United Nations Conference on International Organization to draw up the United Nations Charter.The Charter was signed on June 26, 1945, and the United Nations officially came into existence on October 24, 1945, when the Charter had been ratified by China, France, the Soviet Union, the United Kingdom, the United States and by a majority of other signatories.However, the UN is ineffective due to the Russian and Chinese support of the Syrian dictatorship.Surprise surprise, economic interests are way more important than human life.The model to follow is Operation Desert Storm.To recall, the US assembled a coalition of forces to join it in opposing Iraq’s aggression, consisting of forces from 34 countries, including Argentina, Australia, Bahrain, Bangladesh, Canada, Denmark, Egypt, France, Morocco, New Zealand, Niger, Norway, Oman, Pakistan, Portugal, Qatar, South Korea, Saudi Arabia, Senegal, Sierra Leone, Singapore, Spain, Syria, the United Arab Emirates and the United Kingdom.President Obama should assemble a similar force to oust the brutal Assad regime. The force should include Arab countries. The operation would begin by striking the Syrian army heavily from the sea and from the air. The Syrian opposition coalition is said to have supplied the Americans with a bank of targets.Then follow with a comprehensive ground attack, ensuring Syria won’t fall into the hands of radical Islamists. The US should work together with the moderate elements to install a new government in Damascus. Replacing one evil with another won’t be prudent. The US should work together with the Arab countries and with the Syrian opposition, ascertaining that Syria does not fall in the hands of jihadi terrorists.Toppling the Assad dictatorship without assuring the identity of the successor is a recipe for further bloodshed and instability. The US should take effective means to see that Syria will be governed by people who prefer compromise to violence, who respect human life and who wish Syria to become a respected member of the League of Nations instead of a notorious country on the list of terrorist states.The author (D. Phil., Oxon) is an educator, researcher, human rights activist and director of the Middle East Study Group of the University of Hull, UK. He regularly writes on Israel and Middle East Affairs.