The civil war in Syria is now approaching a crisis point. The crisis, in fact, may already be upon us.

I say “us” because large-scale fighting, not just guerrilla warfare, almost inevitably will involve the United States and its NATO allies. It is a daunting prospect. With startling rapidity, rebel forces have overrun so many military bases, seizing weapons of all kinds, that Damascus no longer looks to be in overall control of the country.

That is probably why the Assad government is now said to be preparing chemical weapons for use against not only the rebels but the regime’s supporters as well, which means tens of thousands of people. That is a red line that Secretary of State Hillary Clinton said this week cannot be crossed without severe consequences. Just what those consequences may be, however, is not entirely clear. Direct and open supply of arms? No-fly zones? Actual air-combat support? Troops on the ground? All these possibilities have the potential for massive and often unintended consequences, including U.S. and NATO casualties.

In the meantime, the war is spreading to Syria’s neighbors, including Lebanon. There was street fighting between Sunnis and Alawites (a Shiite sect) this week in Tripoli, Lebanon’s second biggest city.

The Alawites number about 3 million people, or about 15 percent of Syria’s religiously, ethnically and culturally diverse population of some 20 million. They include Kurds, Armenians, Assyrians, Christians, Druze, Alawite Shias and the more orthodox Sunnis, the last of whom make up a majority of the nation’s people. The Alawites form the backbone of the Assad regime, especially the security services and the essential military units. The Assad family itself is Alawite.

In a highly confessional part of the world, the Alawites fear for their very existence if the rebels topple the Syrian government. At this point, the rebels, mostly Sunnis, are in no mood to be generous, as more than 40,000 people have been killed in the uprising. Moreover, it is not entirely clear who makes up all the rebel groups, even though they were nominally united last month in Qatar as the National Coalition of Syrian Revolutionary and Opposition Forces, now officially recognized by Britain, France, Turkey and the six-nation Gulf Cooperation Council (the Persian Gulf oil states). But the rebel groups were politically united under duress from the West, with arms as the bait. There are almost certainly jihadist groups ready to hijack the rebellion as was almost the case in Libya, where some of the jihadists assassinated the U.S. ambassador and his colleagues, and no doubt is one of the reasons the U.S. has yet to recognize the Syrian rebel coalition.

So Alawite fears are legitimate. If they feel they are forced to flee, where would they go? In 1948 and 1967, the Palestinians fled into neighboring Lebanon, Jordan and Syria, and there has been trouble ever since. But who would take the Alawites, including the Assad family? It is always bottom-line time in the Middle East, where a long and often bloody history has left various ethnic and religious groups with the feeling that their backs are against the sea, and there is nowhere else to go. That is why the Jews and the Palestinians quarrel so bitterly, why the Druze and the Alawites fear for their safety. History has not been kind to minorities, and why, as has been famously noted, there really is no present in the Middle East, only the past repeated over and over again.

The one great virtue of the Assad regime, under both father and son, is that it has been secular, which is why the Christians have been so supportive of an otherwise ruthless dictatorship. But the same was true of Saddam Hussein and his regime, and look what happened to him. Bashar Assad knows the history of his country and the history of the Middle East. It is usually unforgiving, and he does not want to end up at the end of a rope. But if he does, or somehow manages to flee, what kind of Syria would we have? Would it remain geographically united, as it is now, or would it break into Sunni and Alawite mini-states? Would it remain secular or become Islamist? Would Iran retain its toxic influence in Damascus, or would it die on the vine?

All these possibilities are challenges. They are also opportunities. The Chinese, of course, define crisis as a combination of the two. But, then, they have been around for a very long time.

Bill Stewart, a former Foreign Service officer and correspondent for Time magazine, lives in Santa Fe. He writes weekly on current affairs.