Disappointed with the delay in the U.S. decision to launch a strike against the Syrian regime, Israel is bracing for possible consequences. The Israeli air force is on high alert, having taken delivery of a sixth counter-rocket Iron Dome system and preparing to deploy a seventh.

Israeli intelligence agencies do not see a Syrian attack on Israel in response as likely. Still, as Israelis prepared to celebrate Rosh Hashanah Sept. 4-6 and observe Yom Kippur Sept. 13-14, queues for gas masks formed outside the Home Front Command distribution stations. Fearing that a U.S. strike could provoke Syria to launch a chemical attack on Israel, many civilians were rushing to receive personal protection kits provided by the military, with a gas mask and atropine syringe against nerve gas.

Repeated calming messages from the state's leaders did not soothe the public's anxiety. Many Israelis fear that if Syrian President Bashar Al-Assad was not deterred from using chemical weapons against his own people, he might try to use them against Israel as well.

“Israelis should carry on with their daily routine,” declared Prime Minister Benjamin Netanyahu, but at the same time he allowed the Israel Defense Force (IDF) to draft 1,000 reserve servicemen, mostly from the Air Defense Corps. The Israeli air force took delivery of a sixth Iron Dome battery from Rafael and deployed the entire arsenal in northern, central and southern Israel. A seventh battery is expected to be ready for deployment by the time the U.S. is prepared to strike. The Arrow 2 anti-ballistic missile system was placed on high alert, too, as were the Patriot MIM-104 surface-to-air missile batteries.

Syria has already used half its arsenal of Scud missiles in the civil war, but it is believed to still possess a stockpile of 500 Scud B/C/Ds, with ranges of 300, 500 and 700 km (186, 310 and 435 mi.), respectively. While the liquid-propellant Scuds require a long fueling time, which exposes them before launch to potential strike, Israel is more concerned by the Syrian army's vast stockpile of solid-fuel M600 missiles. A clone of the Iranian Fateh-110 missile, the Syrian-made M600 can carry a 500-kg (1,100-lb.) warhead 300 km, which means it could reach all of Israel's population centers and strategic sites. Those, as well as tens of thousands of 302-mm rockets with a range of 150 km, are all capable of carrying chemical warheads.

The Arrow system was originally designed to counter Scud missiles and the Iron Dome to counter short-range rockets. The middle-tier system—David's Sling, which is supposed to deal with medium-range missiles like the M600—is still under development. Israel's Patriot PAC-2s were deployed to fill in this gap, until David's Sling achieves initial operational capabilities. “We do have some capabilities in countering ballistic threats,” commander of a Patriot battalion, Lt. Col. Amir (last name classified), tells Aviation Week.

Israel still considers the Syrian air force a viable threat, despite its constantly degrading capabilities. At Ramat David Air Base in northern Israel, sirens go off every 2 hr., and fighters are sent scrambling, signaling that a Syrian fighter has taken a course toward the Israel border. “The last thing we should do is to underestimate the enemy,” says the commander of an F-16C/D squadron at Ramat David, Lt. Col G. (name classified). “We don't trust luck or coincidence. If there's an aircraft flying toward Israel, we will be there to make sure it will not enter our airspace.”

In its last encounters with the Syrian air force in 1982-86, the Israeli air force scored 100:0 hits. Still, says the commander of an Israeli air force air control unit, Lt. Col Assaf (last name classified), “We monitor [their] every action and take extra precautions, especially in times like this. They still fly. They're operational, and we take them seriously.”

When Syria began receiving advanced Russian air defense systems in recent years, such as the SA-17 (Grizzly/Buk) and the SA- 22 (Greyhound/Pantsyr), the Israeli air force was apparently concerned. After reports on seven strikes the Israeli air force conducted in Syria in 2013, those systems no longer pose a challenge. That is why Israeli intelligence and decision makers confidently believe that Assad would not dare to challenge Israel.

“Assad knows that Israel could swiftly deny him of everything he still has,” a senior Israeli defense source tells Aviation Week. “He would be suicidal to try anything against us, and he's not.” Nonetheless, in the last two weeks the IDF was simulating scenarios of proxy organizations launching rocket strikes against Israel from Syria or Lebanon in response to a U.S. strike.

“We will respond and respond harshly,” Netanyahu has warned repeatedly. Israeli leaders are ambivalent about whether the U.S. should strike Syria. On one hand, they would like the U.S. to decisively enforce the red line it declared. On the other hand, they do not want to see an intervention in Syria that could change the course of the civil war. Israeli leaders consider Assad a bitter enemy, but looking at the Syrian opposition, they fear the alternatives could be worse.