Israel tracks every heavy missile fired in the Syrian civil war, keen to study Damascus's combat doctrines and deployments and ready to fend off a feared first attack on its turf, a senior Israeli military officer said on Thursday.
Colonel Zvika Haimovich of the air defense corps said southward launches against Syrian insurgents by President Bashar Assad's forces gave Israel mere seconds in which to determine it was not the true target - a distinction that could prove crucial for warding off an unprecedented regional conflagration.
"Syria's batteries are in a high state of operability, ready to fire at short notice. All it would take is a few degrees' change in the flight path to endanger us," he told Reuters in an interview at his base in Palmachim, south of Tel Aviv.
Syrian opposition activists say Assad's army has fired dozens of devastating Scud-type missiles at rebel-held areas in the last six months, out of a ballistic arsenal believed to number in the hundreds.
Long-range radars feed real-time data on the barrages to Haimovich's command bunker, where officers brace to activate Arrow II, a US-backed Israeli missile shield that has yet to be tested in battle.
The more threatening launches set off sirens across Palmachim, whose warplanes also await orders to scramble.
Before the more than two-year-old civil war, Israel enjoyed a stable standoff with Syria for decades. Israeli strategists saw little menace in Syria's aging Soviet-supplied military - even from its reputed chemical warheads.
Such complacency is long past. Haimovich said that although Israel was staying out of the Syrian fighting, he and the rest of the top brass were conducting regular battle assessments, including on Assad's missiles launches.
"We are looking at all aspects, from the performance of the weaponry to the way the Syrians are using it. They have used everything that I am aware exists in their missile and rocket arsenal. They are improving all the time, and so are we, but we need to study this, and to be prepared."
He would not detail how Israel determines a missile fired in its direction will not cross the border, saying only that the process took "more than a few seconds, but not much more."
Another Israeli expert, speaking on condition of anonymity, said it combined split-second analysis of the strength of the launch with up-to-date intelligence on Assad's intentions.

Scuds half gone?

Asked about a report on Israel's Channel 10 television that Assad had used up around half of his Scud stockpile against the rebels, Haimovich said: "That sounds credible." But he cautioned that Damascus may have been replenished by its foreign allies.
Haimovich also oversees the Iron Dome short-range rocket interceptor, as well as Israeli coordination with US air defense systems. He described Syria as part of a nebulous northern front with Lebanon, whose Iranian-sponsored Hezbollah militants have been fighting for and armed by Assad.
At least three times this year, Israel has reportedly bombed Syria to destroy what intelligence sources described as advanced weaponry in transit to Hezbollah, which fired 4,000 missiles at the Jewish state in the 2006 Lebanon War. Syria and Hezbollah have hinted at reprisals, a scenario the Israelis assume could spiral to include missile salvoes from Iran and Palestinians in Gaza.
Under such circumstances, Haimovich said, "the Israeli homefront will be hit, but we won't be paralyzed - and I believe we will ensure that by keeping the fight short".
He declined to confirm what Arrow designers have described as its 90 percent shoot-down rate. But he said Israel had beefed up its deployment to more than four nationwide batteries, to allow for repeated interception of any incoming missiles.
"My intention is to ensure that we have at least two opportunities to intercept. We have not yet been called into action on the northern front, but I believe that we will be."
Pointing out a launching ground in Palmachim's sand dunes where towering concrete barricades were being erected to protect future Arrow units, he said: "Our job is to withstand any crisis and deliver the necessary defense."
Israel has fielded five batteries of Iron Dome, which has scored around an 80 percent success rate in intercepting Gaza rockets, the kind of weapons that also feature in Hezbollah's arsenal. Haimovich said a sixth unit would be deployed soon.
A more powerful version of Iron Dome, known as David's Sling or Magic Wand, performed well in its first field trial in November and prompted some Israeli officers to predict it could be ready for use this year. That would bolster the multi-tier missile defense program.
Haimovich said he knew of no such plan but that Iron Dome, Arrow and their US counterparts already provided Israel with an adequate "protective umbrella".