The IDF’s top intelligence analyst said Tuesday that the army was quite certain that President Bashar Assad deployed chemical weapons against rebel forces in Syria on March 19.

“To the best of our understanding, the regime used lethal chemical weapons,” said Brig. Gen. Itai Brun, head of the Research and Analysis Division at the IDF Military Intelligence Directorate.

Speaking at a security conference in Tel Aviv, Brun said further that based on the pictures of the victims — the size of their pupils, “and the foam coming out of their mouths” — the army believed that Assad’s troops had used the lethal nerve gas sarin as a weapon.

Sarin, used by Saddam Hussein in aerial strikes against Iraqi Kurds in 1988 and in a Japan terror attack in 1995, is a nerve agent that cripples the respiratory system. It is hundreds of times more toxic than cyanide and is considered a weapon of mass destruction.

Secretary of Defense Chuck Hagel said Monday during a visit to Israel that “the Syrian government’s use of chemical weapons would be a game changer.”

Also on Monday, Defense Minister Moshe Ya’alon described three red lines for Israel on Syria — the transfer of sophisticated weapons systems to rogue elements, the violation of Israel’s sovereignty along the border, and the rebels’ acquisition of chemical weapons. “We are ready to operate if any rogue element is going to put his hands [on chemical agents] or any chemical agents are going to be delivered to rogue elements in the region,” he said.

Brun said that in Syria today there are over 1,000 tons of chemical weapons, including sarin and VX, both of which can be deployed from artillery rounds and long-range ballistic missiles.

Chemical weapons have been used on more than one occasion in Syria, and the world’s persistent reluctance to act in response to the use of those weapons is typical of the major powers’ current approach to the tremors shaking the Middle East, he said.

Brun described US hegemony as “dominant but eroding” and said that the world powers “prefer to focus elsewhere but are sucked into the Middle East.”

Pointing to a slide featuring three images — of ineffectual UN observers in Syria, of a dead Muammar Gadaffi splayed on the hood of a jeep and of the P+5 talks with Iran — he said all three depicted situations in which world involvement “did not attain achievements.”

The region, he said, is undergoing “architectural changes” that will likely not stabilize in the coming years. Dominant among them has been the rise of Sunni Islamist parties, the shifting nature of global jihad and the weakening of the Iran-Syria alliance. Worsening economic conditions, unprecedented sanctions and upcoming national elections in June have weakened Iran’s position and created “an interesting gap” between Iran’s capabilities and its progress in advancing its nuclear program.

“This is not a good time for Iran,” he said, adding that the regime would likely neither forgo its nuclear program nor break out for the bomb in the coming year.

It is clear, though, that the Sunni Islamist movements are ascendant and that the Salafist global jihad has changed its outlook. Perched on either side of Israel, he said, “their agenda has become more local, regional.”

And though the dwindling threat of a standard military attack on Israel has lowered the overall security risk to the country, it has also brought new challenges to the fore. Referring to the surprise attack in October 1973, he said, “We also have to be prepared for a cyber Yom Kippur [War].”

The host of the Institute for National Security Studies conference, former head of military intelligence Amos Yadlin, asked Brun which side in the internal conflict represented the greater danger in terms of chemical weapons.

“We should be very, very worried about them falling into the hands of those who do not conduct gain-loss considerations,” Brun said of the jihadist groups of rebels.