Syria’s embattled President Bashar al-Assad is sitting on a powder keg of angry citizens who want his brutal regime to end. He also sits on the Arab world’s most lethal arsenal of weapons of mass destruction, hundreds of chemical warheads and dozens of Scud missiles that can deliver them anywhere in the Levant.

Like almost everything else in Assad’s Syria, the arsenal of chemical weapons and missiles is a legacy of his father Hafez al-Assad. After the Syrian army and air force were defeated by Israel in Lebanon in 1982, the elder Assad ordered development of a chemical arsenal to provide a deterrent against the Israelis. Syrian scientists developed an effective chemical weapons program using the nerve agent sarin, which is 500 times more toxic than cyanide and was discovered by German scientists in the 1930s. In 1988 Saddam Hussein used sarin in his war against the Iranians and in attacks on Iraqi Kurds, with devastating impact.

Syria mated the nerve agent with Scud missiles acquired from the Soviet Union in the mid-1980s. When Israel learned of the Syrian weapons, it considered military action to destroy the program but concluded it was too developed and too disbursed to be susceptible to air attacks without an unacceptable risk that Syria would respond by firing chemicals into Tel Aviv. Instead Israel embarked on building an anti-tactical ballistic missile program called Arrow.

Hafez al-Assad apparently also began Syria’s nuclear weapons program shortly before his death. When Israel and the United States learned of this program in 2007, Israel decided to act. On Sept. 6 of that year, the Israeli air force destroyed Syria’s nascent nuclear facility in al Kibar. The CIA released a video about the facility in April 2008 that demonstrated it was a North Korean-built, gas-worked, graphite-moderated nuclear reactor designed to produce plutonium for nuclear weapons. It was a clone of North Korea’s Yongbyon reactor. After the raid the Syrians bulldozed the site and have since blocked inspection by the International Atomic Energy Agency.

Would Bashar al-Assad use chemical weapons against a NATO military operation like the one that assisted the Libyan opposition? Almost certainly he would. He clearly has few scruples about mass murder, and foreign air bases would be a logical target for Scuds. He also might be tempted to use them against Israel in a desperate, Samson-like move to destroy his enemies. Scuds are notoriously inaccurate, and cities are much easier targets than airfields.

Would he use them against his own people? Would his army support such a move? This is harder to know. His fellow Baathi Saddam used them on Iraqi Kurds. Using them on Syria’s Sunni Muslim majority would antagonize the entire world and set Assad and his cronies up for war crimes trials. It would mean terrible reprisals by the Sunni sooner or later.

If Syria collapses into chaos over the next few weeks and months, or the army splits between Assad’s fellow Alawi Muslims and the majority Sunnis, a key question will be the fate of these chemical weapons and their delivery systems. Terrorist groups, such as Assad’s friends Hezbollah and Hamas, would love to get sarin warheads. Whether they could maintain and use them is another question. Chemical weapons in amateur hands can be very dangerous both to the amateur and his enemy.

The fact of Syria’s chemical and missile arsenal is well known to NATO governments. There is no reason it should discourage support for ending the Assad dictatorship. It does, however, argue for caution in how to do so.