John Mueller has written an article (Erase the Red Line: Why We Shouldn't Care About Syria's Chemical Weapons) in which he discusses how (not) dangerous chemical weapons really are.
As it happened, chemical weapons accounted for considerably less than one percent of the battle deaths in the [World War I], and, on average, it took over a ton of gas to produce a single fatality. Only about two or three percent of those gassed on the Western front died. However, the British government initially exaggerated its deadliness as that proved to be a good argument to draw the US into the war.
The article also discusses Halabja. It mentions that the people visiting the city after the gas attack saw only a few hundred dead. The number of 5000 that is commonly used comes from Iranian sources and very likely includes victims from attacks with conventional weapons at the same time.
The effectiveness of poison gasses as a weapon is low: According to Iranian reports, of the 27,000 Iranians gassed through March 1987, only 262 died.. After World War I some considered it even a humane weapon as it incapacitated so many soldiers while killing so few.
The term "weapons of mass destruction" comes from an American law from 1992 (expanded in 1994) that gives a very broad definition of the term that even includes some explosives.
Hacked e-mails reveal 'Washington approved' plan to stage Syria chemical attack: the article talks about a hacked email account of the British private defense contractor Britam Defence. According to the article there was an offer from Qatar - that claimed to have US approval - to stage a chemical weapon incident in Syria with chemical arms from Libya. Qatar would offer lots of cash for it. Britam later forced the Daily Mail to publish that it accepted the mail (retracting a prior article) to be a fraud and to pay a damage. The mail is supposed to be a changed version of a real email.
Turkey finds sarin gas in homes of suspected Syrian Islamists – reports. Later Turkey claimed that it was antifreeze. But why would they transport antifreeze in spring?
6 December 2012: Shock Video Shows ‘Syrian Rebels’ Testing Chemical Weapons: This video claims to show rebels testing chemicals arms on rabbits.
9 December 2012: Sources: U.S. helping underwrite Syrian rebel training on securing chemical weapons:
February 2013: Syria, the Saudi connection: The Prince with close ties to Washington at the heart of the push for war: It was Prince Bandar’s intelligence agency that first alerted Western allies to the alleged use of sarin gas by the Syrian regime in February.
19 March 2013: This is the date of the Khan al-Asal attack, extensively discussed by Global Research. Carla del Ponte later concluded the attack was most likely by the rebels. Indications were that it likely was done with an improvised missile and that the sarin seemed home-made. In July Russia provided the OPCW with a 100 page report to support its claim that the rebels did it. The first US reaction was denial.
20 March 2013: Syrian Rebels Caught on Tape Discussing Chemical Weapons Attack: An alleged audio recording of a phone conversation between two members of the Free Syrian Army contains details of a plan to carry out a chemical weapons attack capable of impacting an area the size of one kilometer.
24 March 2013: Jihadists, not Assad, apparently behind reported chemical attack in Syria: Intelligence reports suggest jihadists among the Syria rebels have technical know-how to produce chemical warheads.
24 May 2013: Russian journalists have proof Syrian insurgents used chemical weapons: Russian journalists who were on assignment in Syria have handed the United Nation Secretariat videos showing chemical weapons attacks allegedly committed by opposition fighters in the vicinity of Aleppo on March 19. This was confirmed by the spokesman for the Deputy Secretary General Farhan Haq.
Read more: http://english.ruvr.ru/news/2013_05_24/Russian-journalists-have-proof-Syrian-insurgents-used-chemical-weapons-089/
27 May 2013: Chemical warfare in Syria: this is a much quoted article of some French journalists who were embedded with the rebel fighters for some time and say they witnessed use of chemical arms by the government.
31 May 2013: Reports claim Al Nusrah Front members in Turkey were planning sarin gas attacks
2 June 2013: Iraq claims foiling al-Qaeda nerve-gas plot: Ministry says cell working for group planned attacks with remote-controlled planes in Iraq, Europe and North America.. See also the Iraq uncovers al-Qaeda 'chemical weapons plot'
14 June 2013: U.S. Is Said to Plan to Send Weapons to Syrian Rebels: Mr. Rhodes said there was no reason to think that the resistance has access to chemical weapons. “We believe that the Assad regime maintains control of these weapons,” he said. According to a C.I.A. report, which was described by an American official who declined to be identified, the United States has acquired blood, urine and hair samples from two Syrian rebels — one dead and one wounded — who were in a firefight with Syrian government forces in mid-March northeast of Damascus. The samples showed that the rebels were exposed to sarin..
17 June 2013: Analyst: Al Qaeda affiliate in Syria now best-equipped of the group: With the growing strength and support for al-Nusra, U.S. concerns are growing about its influence to further destabilize Syria and potentially pose a greater regional threat, administration officials have told CNN. "They are making desperate attempts to get chemical weapons," the analyst told CNN, noting that in the past few weeks, security services in Iraq and Turkey arrested operatives who were "trying to get their hands on sarin."
17 June 2013: Groundwork for arming Syrian rebels began before Obama’s announcement: several weeks before the announcement there were already signs on the ground in Jordan that the US was going to arm the rebels.
20 June 2013: In Syrian chemical weapons claim, criticism about lack of transparency: Jean Pascal Zanders, who until recently was a research fellow at the European Union Institute for Security Studies, said he has scoured the Internet for photographs, video and news reports documenting alleged nerve agent attacks in Syria. What he has seen has made him a skeptic. Few of the photographs, Zanders said, have borne the trademark symptoms of a chemical weapons attack. In a paper he presented last week to the E.U. Non-Proliferation Consortium, he compared photographs documenting Iraq’s 1998 chemical weapons attack against Kurds in the town of Halabja. The Halabja victims appeared to have died instantaneously from chemical agents, he said, and their bodies showed telltale signs of exposure to sarin: blue lips and fingertips caused by suffocation and a pink hue brought on by excessive sweating and high blood pressure. “No press reports from Syria refer to those descriptions, which is one of the reasons why I am skeptical about those reports,” he said.
10 July 2013: Russia says it has evidence that Syrian rebels used sarin gas in deadly attack: He says the inquiry has established that the rebels fired a missile containing the nerve agent sarin at the town of Khan al-Assal. The attack killed 26 people including 16 regime troops. "The results of the analysis clearly indicate that the ordnance used in Khan al-Assal was not industrially manufactured and was filled with sarin," Mr Churkin said. See also Russia Says Syrian Rebels Used Sarin Gas
16 July 2013: Syrian rebels' Damascus chemical cache found by Assad army - State TV: a rather vague story that doesn't provide more identification than that the found chemicals are "corrosive".
22 July 2013: The rebels overran Al-Assal and murdered 123 Syrians. According to some the aim was to eliminate witnesses of the chemical attack.
26 July 2013: Iraqi security shuts down al-Qaeda chemical weapons plants: Security services shut down two plants, "one in Baghdad and the other in an area near the capital," and confiscated chemicals and the equipment used to manufacture them, the ministry said.
The cell had reached an advanced stage in the manufacture of extremely dangerous chemical weapons – sarin, mustard and VX nerve gases -- as well as a highly toxic, incendiary chemical liquid, al-Askari told Mawtani.
26 August 2013: Exclusive: CIA Files Prove America Helped Saddam as He Gassed Iran
29 August 2013: Verify chemical weapons use before unleashing the dogs of war: According to the doctored report, the chemical attack was carried out by the 155th Brigade of the 4th Armored Division of the Syrian Army, an elite unit commanded by Maher al-Assad, the president’s brother. However, the original communication intercepted by Unit 8200 between a major in command of the rocket troops assigned to the 155th Brigade of the 4th Armored Division, and the general staff, shows just the opposite. The general staff officer asked the major if he was responsible for the chemical weapons attack. From the tone of the conversation, it was clear that “the Syrian general staff were out of their minds with panic that an unauthorized strike had been launched by the 155th Brigade in express defiance of their instructions,” the former officers say. According to the transcript of the original Unit 8200 report, the major “hotly denied firing any of his missiles” and invited the general staff to come and verify that all his weapons were present. The report contains a note at the end that the major was interrogated by Syrian intelligence for three days, then returned to command of his unit. “All of his weapons were accounted for,” the report stated.
3 September 2013: Syria Defector 'Exposes Assad Chemical Attack': Abdeltawwab Shahrour, head of the forensic medicine committee in Aleppo, claims there was a chemical attack in Khan al-Assal, Aleppo, on March 19, said Istanbul-based opposition coalition spokeswoman Sarah Karkour. Mr Shahrour, who has defected to Turkey, has documents proving the attack took place and eyewitness accounts from police authorities that contradicte the administration's version of events, a second opposition official said. Dr Shahrour was expected to reveal the details of the attack during a press conference in Turkey but Syrian National Council spokesperson Khaled Saleh said he was unable to appear due to "security concerns". Mr Saleh added that the national council has received information in the last few days that three government convoys were carrying chemical weapons and one had reached a military airport. He said: "We have serious concerns based on the information that we have received from sources inside the Assad army who are sympathetic to the revolution that Assad might be considering using those chemical weapons against innocent civilians."
7 September 2013: On Syria Vote, Trust, but Verify. This is an Op-Ed article written by a member of Congress: THE documentary record regarding an attack on Syria consists of just two papers: a four-page unclassified summary and a 12-page classified summary. [..] In fact, even gaining access to just the classified summary involves a series of unreasonably high hurdles. We have to descend into the bowels of the Capitol Visitors Center, to a room four levels underground. Per the instructions of the chairman of the House Intelligence Committee, note-taking is not allowed. Once we leave, we are not permitted to discuss the classified summary with the public, the media, our constituents or even other members. Nor are we allowed to do anything to verify the validity of the information that has been provided. And this is just the classified summary. It is my understanding that the House Intelligence Committee made a formal request for the underlying intelligence reports several days ago. I haven’t heard an answer yet. And frankly, I don’t expect one.
7 September 2013: First on CNN: Videos show glimpse into evidence for Syria intervention: Obama is now showing Congress in closed sessions some videos. Those as shown here. The CIA should have verified them.
7 September 2013: Obama’s Battle for Syria Votes, Taut and Uphill: On the day the president is speaking, the American Israel Public Affairs Committee plans to blanket Capitol Hill with 250 advocates, having already contacted dozens of lawmakers to urge them to support a strike. The advocates will carry a simple message, according to a person involved in the effort: Syria is a proxy for Iran, and the failure to enforce Mr. Obama’s “red line” against the use of chemical weapons by Mr. Assad will be interpreted in Tehran as a sign that he will not enforce a red line against the production of nuclear weapons by the Iranian government. Israel itself is staying out of what it regards as a domestic American political debate. But Michael B. Oren, the Israeli ambassador to the United States, said he was telling any lawmaker who expressed fears that Syria would attack Israel in retaliation for an American missile strike: “Don’t worry about us. We can defend ourselves.”
1 September 2013: Unwieldy For Weapons Use In Syria, Sarin Is A Bogeyman: article by Yoichi Shimatsu who previously reported about the sarin attack in the Tokyo subway. He claims it was not sarin but mustard gas. He believes sarin is much too deadly to have been used either in Tokyo or in Syria. The detected sarin traces are according to him more likely other organophosphates that are used as agricultural chemicals. If farmers have such materials, why shouldn't they use them in a war?
4 November 2011: Libyan chemical weapons stockpile intact: inspectors: Libya had many chemical weapons and not all had been declared with the UN. Some may have been shipped to Syria.
The Chemical Weapons Convention dates from 1993. 189 countries have ratified it. Syria did not sign this treaty.
The Chemical Weapons Treaty of 1925 (a.k.a. Geneva Protocol) forbids the use of chemical weapons in war. It does not forbid it in civil war or when the other side uses it. Syria signed this treaty.