It is a matter of time before Aleppo, the second largest city in Syria, falls to the hands of the Assad regime. While the American-led coalition airstrikes hit ISIS targets in Iraq and Syria, Mr. Assad continues his bloody attacks on Aleppo. Over the last two months, the Assad regime intensified its attacks on the city, expanding its control from air and land, and forcing the Syrian rebels further north. It has more interest in capturing Aleppo than defending Kobani.Staffan de Mistura, the U.N.'s special envoy to Syria, who on Nov. 10 proposed to "freeze" fighting in Aleppo, described it as a first step toward a wider solution. Though well-intentioned, the proposal does not explain what that wider solution is. It does not even amount to a formal call for a cease-fire. The Syrian opposition fears that the Assad regime will use it to its advantage to gather strength and launch new attacks.As BBC reported, "the regime, scenting victory, is certain to refuse to stop its advance unless the situation is "frozen" to its clear advantage." There is no doubt that Damascus will manipulate the U.N. proposal. Not surprisingly, the Free Syrian Army (FSA) rejected the proposal, saying that it will only serve the Assad regime.One FSA commander explained: "We learned not to trust the Assad regime because they are cunning and only want to buy time. We saw what happened in Homs and we will never accept the same scenario in Aleppo." The U.N. should not give another opportunity to the Assad regime to buy time.The attacks against ISIS under the U.S. strategy are justified and should continue. But they are also working to the advantage of the Assad regime. ISIS serves as a useful distraction to divert attention from the main issue, which is the Assad regime's brutal war against the Syrian people. It is this prolonged war that has prepared the ground for the rise of ISIS. Even U.S. Defense Secretary Chuck Hagel is reported to have said that the airstrikes are benefitting the Assad regime. The claims that President Obama's secret letter to Ayatollah Ali Khamenei, sent in October to boost the ongoing nuclear talks between Iran and P5+1, promised not to attack the Assad regime, only complicates the matter and raises further questions about the intentions of the U.S. strategy in the eyes of the Syrian opposition. For weeks, Western media outlets presented Kobani as a test for the success or failure of the U.S. strategy in Syria. This hype was misguided from the very beginning. While it is important to stop ISIS in Kobani, the real test for the international community is to help the Syrian opposition defend the historic city of Aleppo against the Assad regime and ISIS.If Aleppo falls, this will be strategic defeat not only for the Syrian rebels but also for the U.S.-led coalition that promised but failed to provide aid to the Syrian rebels. In an op-ed published on Nov. 3, 2014, French Foreign Minister Laurent Fabius noted that "abandoning Aleppo would mean condemning Syria to years of violence. It would mean the death of any political future." Mr. Fabius is right. Aleppo is the symbol of a pluralistic, non-sectarian, democratic and united Syria. Its fall would be a victory for tyranny and defeat for the Syrian people.The fall of Aleppo would also add new layers of pain and misery to the already horrible humanitarian situation in Syria. Only two years ago, Aleppo was a city of 1.5 million people. If the city falls, the 300,000 men, women and children who have stayed in the city, would be forced to migrate to Turkey, only 60 kilometers away. The fall of Aleppo would also send a chilling message to the Syrian people: youtarget="_blank"'>