International disarmament experts began the mammoth task of destroying Syria's chemical arsenal on Sunday under a hard-won deal that averted threatened US military action following an August 21 gas attack.
The team from the Organisation for the Prohibition of Chemical Weapons (OPCW) arrived in Syria on October 1 to launch its mission to destroy the decades-old arsenal under the terms of a landmark UN Security Council resolution passed unanimously on September 28.
The task is huge, as Syria's arsenal is believed to include more than 1,000 tonnes of sarin, mustard gas and other banned chemicals stored at an estimated 45 sites across the war-torn country.
The mission is the first in OPCW history to take place in a country wracked by civil war.
President Bashar al-Assad's regime is accused of using chemical weapons in attacks on two rebel-held areas near Damascus that US intelligence and the Syrian opposition charge killed hundreds of people.
On September 1, US Secretary of State John Kerry said Washington had clear intelligence proving sarin gas was used in the August 21 assault by regime forces.
A French intelligence report released on September 2 said there was "massive use of chemical agents" on the day of the attacks in Syria and that only the regime could have been responsible.
The report said Syria "had one of the biggest operational stocks of chemical weapons," including an arsenal of more than 1,000 tonnes comprising sarin and mustard gas and more powerful neurotoxic agents.
It also said Syrian scientists were working on more lethal nerve agents.
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The Syrian regime acknowledged for the first time on July 23, 2012, that it had chemical weapons and threatened to use them in case of a Western military intervention, but never against the Syrian population.
One of the few countries not to have signed the Chemical Weapons Convention until last month, Syria began its chemical weapons programme in the 1970s with the help of Egypt and the then Soviet Union.
In March this year, the government and the rebel forces battling to topple it accused each other of using chemical weapons in the more than two-year conflict.
Britain, France and the United States have accused Syrian forces of using chemical weapons against insurgents on several occasions.
Russia, a key ally of Syria along with Iran, has said it has proof sarin gas was used by the rebels.
In the 1990s, Moscow provided Syria with support for the programme, followed by Tehran since 2005, according to the Nuclear Threat Initiative (NTI), an independent organisation tracking data on weapons of mass destruction.
An analyst at the non-proliferation and disarmament programme of the International Institute for Strategic Studies (IISS) says Syria has the biggest chemical weapons programme in the Middle East, launched with the goal of counterbalancing Israel's nuclear programme.
On September 26, the Washington Post reported that a confidential Russian-US assessment of Syria's chemical arsenal revealed that much of it was unweaponised, making it easier to destroy.
On January 30, Israeli warplanes bombed a ground-to-air missile battery and adjacent military complex near Damascus suspected of holding chemical weapons, with Israel saying it feared their transfer to Lebanon's Shiite militant group Hezbollah, according to a US official.
According to The New York Times, the raid could have damaged Syria's main research centre into biological and chemical weapons.