On the ninth of March 2014, the Syrian opponent inaugurated military fighting called (Battle of Khan Shaykhun – Gate of Hama). To govern the strategic city, which was the only supply line for the Syrian regime forces in the two camps, Wadi al-Dhaif and al-Hamidiya in the countryside of Maarat Al-Numan.
It was only a few days before the opponent managed to regulate the essential military points of the Syrian regime forces around the city, encompassing (Al-Ghadeer checkpoint, Al-Marzafi, Al-Harash, Al-Syriatel, and Dahrat al-Nimr gathering).
Almost 80% of Khan Shaykhun reached under the control of the armed opposition.
The chance of recovering the city became Reaching Wadi Deif camp is much weaker than before.
Besides, on April 4th, 2014, the opposition strikes undertook a battle that tightened the rope on the regime forces in the Hamdiyeh and Wadi al-Dhaif camps on the one hand (Tell Mannas, Altah, Ma`arshamin, and Dayr al-Sharqi). It managed through battle, so that prevailed for two weeks to control various towns, including (Babolin and Al-Salihiya and Kafrbassin), which led to the destruction of the regime forces in the Hamidiya camp, which provoked him to use unconventional weapons on April 21st, 2014.
Reports received at the time of a toxin gas attack on the town of Tell Mannas, which was a back-up supply line for the opposition forces fighting on the Wadi al-Dhaif front in the southern Idlib governorate.
After collecting these reports, the teams of the Chemical Violations Documentation Center in Syria/ CVDCS begins to move immediately to collect information, witnesses and biological and environmental samples necessary to present them to the relevant international missions the Fact-Finding Mission (FFM), which in turn interviewed the witnesses and the injured and worked on analyzing these samples in laboratories that the organization in The Hague was later able to establish a toxic chlorine gas attack without specifying who was responsible for it.
In 2015, theJoint Investigative Mechanism (JIM) formed by UN Security Council Resolution No. 2235, and the Mechanism opened a criminal investigation into the incident, CVDCS and many Syrian and human rights organizations worked to provide all aspects of support to the Mechanism that issued its first report in October 2016 and clarified the story that distributed to Membership of the UN Security Council,
The Syrian military helicopters dropped chlorine gas on two towns in Idlib Governorate in northwestern Syria, They are Tell Mannas in April 2014 and Sarmin on March 16th, 2015, and said that the Islamic State “ISIS” was responsible for the use of chemical weapons in the countryside of Aleppo on August 21st 2015.