Unnamed officals from U.S. and Israeli intelligence agencies reportedly claim that intercepted communications involving top Syrian officials prove that the Syrian government was responsible.
Noah Shachtman of Foreign Policy reports that U.S. intelligence services overheard an official at the Syrian Ministry of Defense exchanging "panicked phone calls with a leader of a chemical weapons unit, demanding answers for a nerve agent strike that killed more than 1,000 people" and caused"neurotoxic symptoms" in thousands.
On Saturday the German magazine Focus, citing a former Mossad officer, reported that Israel's electronic intelligence Unit 8200 intercepted the communication of the Syrian army during the attack.
"The analysis has clearly shown that the bombardment with poison gas missiles was made by Syrian government forces," according to the officer.
Shachtman also reports that it was unclear who ordered the attack, citing a U.S. intelligence official who wondered if there was a "sort of general blessing to use these things" or if each attack requires specific orders from the top.
"We don't know exactly why it happened," the official told FP. "We just know it was pretty fucking stupid."
Other reported evidence
Arab diplomats told The Wall Street Journal that Israeli spy services provided the CIA with "intelligence from inside an elite special Syrian unit that oversees Mr. Assad's chemical weapons" indicating that certain types of chemical weapons were moved near the Eastern Ghouta region of the capital in advance of the attack. The U.S. spy agency reportedly verified the intel.
U.S. officials told WSJ that Mr. Obama's aides reviewed satellite images that officials said showed how continued shelling by the Syrian army — which was launching "Operation City Shield" against rebel positions in the area — destroyed evidence of chemical-weapon use.
Syrian weapons expert and blogger Eliot Higgins has done extensive analysis on intact rocket shells found at the site of the apparent attack and noted that "a high explosive warhead ... would serious damage the rocket on impact."
FP's intelligence source and his colleagues reportedly came to the conclusion that the weapon was filled with nerve agent as opposed to a conventional explosive.
"Why is there so much rocket left? There shouldn't be so much rocket left," the intelligence official told FP.
Higgins concluded that the evidence seems to "strongly indicate the munition was fired from the north, where 6-8km away you'll find a number of military installations, connected by a 2km road to the 155th Brigade missile base."
The decision to strike
Taken together, the information convinced the administration that Assad's forces had used chemical weapons against its own people. France, the UK, and Germany as well as Turkey back U.S. military action.
Last week a Reuters poll found that about 60% of Americans are against any type of U.S. intervention in Syria, while just 9% support it.
The White House reportedly plans to announce at least some of its evidence before taking any military action.
David Kirkpatrick and Mark Landler of The New York Times report The Arab League said that "responsibility falls on the Syrian regime" but did not support retaliatory military action by the U.S.
The New York Times notes that "Egypt, still the most populous Arab state with the largest Arab military, disagreed" with Saudi Arabia over explicitly condemning Mr. Assad for launching the attack. (Such a condemnation would help the West justify military action.)
Nevertheless, Obama administration officials told The Times that they were satisfied with the Arab League statement.
Cruise missiles
Any attack would likely be limited, reportedly involving a barrage of sea-launched cruise missiles from four Arleigh Burke-class destroyers in the eastern Mediterranean and lasting no more than two days.
On Tuesday The New York Times, citing U.S. officials, reported that the "the initial target lists included fewer than 50 sites, including air bases where Syria’s Russian-made attack helicopters are deployed."
On Tuesday State Department spokeswoman Marie Harf said that the goal of the operation would “not about regime change.”
UN approval
On Wednesday UN envoy Lakhdar Brahimi said it seemed that "some kind of substance" had been used near Damascus on August 21, but emphasized that any U.S. military action would need to be approved by the United Nations Security Council.
The UK has drafted a resolution to be put forward to the United Nations Security Council, which includes two countries — China and Russia (which has backed Assad from the beginning) — that have blocked any previous actions against Assad.
On Tuesday Kevin Baron of Defense One reported that the U.S. has decided that it does not need UN or NATO approval for a strike.
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