What's the evidence of Syrian chemical weapons attack?
 A Free Syrian Army fighter looks through a hole from behind sandbags, while a fellow fighter reads the Quran in Deir Ezzor, Syria, on Tuesday, September 3. The United States and other Western nations blame the Assad regime for a chemical weapons attack that's believed to have killed more than 1,400 people. Tensions in Syria began to flare in March 2011 and escalated into an ongoing civil war. Click through to view the most compelling images taken since the start of the conflict:  A Free Syrian Army fighter takes cover as he watches forces loyal to President Bashar al-Assad near Hanano barracks in Aleppo on September 3.  A Free Syrian Army fighter is seen through a hole in a wall of a building in Aleppo on September 3.  Free Syrian Army fighters walk inside a damaged house in Aleppo on September 3.  A Free Syrian Army fighter walks through a hole in a wall in Aleppo on September 3.  Free Syrian Army fighters talk inside a burnt house in Aleppo on September 3.  A Free Syrian Army fighter peeks through the curtains of a bedroom in Deir ez-Zor, Syria, on Monday, September 2.  Free Syrian Army fighters take their positions behind piled sandbags, as one of them points his weapon, in Deir ez-Zor on September 2.  A rebel fighter points his weapon at Syrian regime forces in Deir ez-Zor on September 2.  Syrian firefighters try to extinguish a fire after a missile hit a residential building in Damascus, Syria, on September 2.  A U.N. arms expert collects samples during an inspection of a suspected chemical weapons strike site in the Ghouta area outside Damascus on August 29.  People search for belongings in rubble in Raqqa, Syria, on August 29.  Free Syrian Army fighters launch a rocket toward forces loyal to Syrian President Bashar al-Assad in Deir Ezzor on August 29.  A Syrian Kurd uses hay to hide another woman in a training session organized by the Kurdish Women's Defense Units on Wednesday, August 28, in a northern Syrian border village. They're preparing if the area comes under attack.  Free Syrian Army fighters escort U.N. vehicles with chemical weapons experts on August 28 through a site of a suspected chemical weapons attack outside Damascus.  A Free Syrian Army fighter takes position behind sandbags in the old city of Aleppo, Syria, on Tuesday, August 27.  A U.N. team leaves its Damascus, Syria, hotel in a convoy on Monday, August 26. The team was to investigate an alleged chemical attack that killed hundreds last week in a suburb of the Syrian capital. Sniper fire hit a vehicle used by the U.N. chemical weapons investigation team multiple times Monday, according to the United Nations.  A Syrian soldier walks down a street in Damascus on Saturday, August 24.  Pigeons lie dead on the ground on August 24 from after what activists say is the use of chemical weapons by government forces in the Damascus suburb of Arbeen.  Columns of smoke rise in Barzeh after heavy shelling on Friday, August 23.  A young Free Syrian Army fighter is reflected in a mirror as he takes position in a house in Aleppo on Thursday, August 22.  Rebels move around a building in Aleppo on August 22.  Syrian rebels claim pro-government forces used chemical weapons to kill citizens outside Damascus on Wednesday, August 21. People inspect bodies in this photo released by the Syrian opposition Shaam News Network.  People search the rubble of a bombed building in Aleppo, Syria, on Friday, August 16.  Men bury the bodies of six members of the same family killed in a bombing in Raqqa on Saturday, August 10.  Syrian Army soldiers patrol a devastated street in Homs on Wednesday, July 31.  Free Syrian Army fighters move through a hole in a wall in Khan al-Assal on Monday, July 22, after seizing the town.  A rebel fighter walks past swings in a deserted playground in Deir al-Zor, Syria, on Sunday, July 21.  A rebel fighter speaks with a fellow fighter through a hole in a wall in Deir al-Zor on July 21.  A Free Syrian Army fighter casts a shadow on a wall as he carries his weapon in a shelter in Deir al-Zor on Thursday, July 18.  Yahya Sweed, 13, is comforted by his father as he lies on a bed in Kfar Nubul on Tuesday, July 16. The boy was injured by shrapnel, resulting in the amputation of his right leg.  A rebel fighter naps in a trench about 300 feet from the Syrian government forces' positions along the highway connecting Idlib with Latakia on Monday, July 15.  A rebel fighter uses a hole in the wall of a destroyed school to aim at Syrian government forces in the Izaa district of Aleppo on Sunday, July 14.  A Free Syrian Army fighter uses a mirror to scope out snipers loyal to Syrian President Bashar al-Assad in Aleppo on Friday, July 12.  A Free Syrian Army fighter stands over a boy who was injured during shelling in Al-Bara on Monday, July 8.  Members of the Free Syrian Army fire a homemade rocket toward regime forces in Deir al-Zor on Sunday, June 16.  Syrian rebels leave their position in the northwestern town of Maaret al-Numan on Thursday, June 13. The White House said that the Syrian government has crossed a "red line" with its use of chemical weapons and announced it would start arming the rebels.  Forces loyal to Syrian President Bashar al-Assad are seen near Qusayr on Thursday, May 30.  Syrian rebels take position in a house during clashes with regime forces in the old city of Aleppo on May 22.  Syrian army soldiers take control of the village of Western Dumayna north of the rebel-held city of Qusayr on Monday, May 13. Syrian troops captured three villages in Homs province, allowing them to cut supply lines to rebels inside Qusayr town, a military officer told AFP.  Rebel fighters fire at government forces in the northern Syrian city of Aleppo on Sunday, May 12.  Searchers use a flashlight as they look for survivors among the rubble created by what activists say was a missile attack from the Syrian regime, in Raqqa province, Syria, on April 25.  A Kurdish fighter from the "Popular Protection Units" (YPG) takes position inside a building in the majority-Kurdish Sheikh Maqsood area of Aleppo, on Apri. 21.  People walk past destroyed houses in the northern Syrian town of Azaz on Sunday, April 21.  Free Syrian Army fighters take positions prior to an offensive against government forces in the Khan al-Assal area, near Aleppo on Saturday, April 20.  Men inspect damage at a house destroyed in an airstrike in Aleppo on April 15.  Syrian and Kurdish rebel fighters walk in the Sheikh Maqsud district of Aleppo on April 14.  A female rebel monitors the movement of Syrian government forces in Aleppo's Sheikh Maqsud neighborhood on Thursday, April 11.  A rebel runs to avoid sniper fire from Syrian government forces in Aleppo on April 11.  Syrian rebels observe the movement of Syrian government forces around Al-Kendi hospital in Aleppo on Wednesday, April 10.  Rescue teams and security forces check out the scene of a deadly car bomb explosion in Damascus on April 8.  The fighting has taken a toll on buildings in Aleppo's Saladin district, seen here on April 8.  A Syrian rebel runs for cover in Deir ez-Zor on April 2.  A rebel checks for snipers across the street toward the Citadel in Aleppo, Syria, on Saturday, March 30, in this photo taken by iReporter Lee Harper.  A Free Syrian fighter mourns the death of a friend in Aleppo on March 30, in this photo taken by iReporter Lee Harper.  A Syrian opposition fighter runs for cover from Syrian army snipers in Aleppo on Wednesday, March 27.  A Syrian girl covers her face to protect herself from fumes as a street covered with uncollected garbage is fumigated in Aleppo on Sunday, March 24.  A Syrian man and his family drive past damaged buildings in Maarat al-Numan, on Wednesday, March 20.  Syrians carry the body of a Syrian army soldier during a funeral ceremony in Idlib province on Tuesday, March 19.  Syrian rebels take position in Aleppo, the largest city in the country, on March 11.  Syrian men search for their relatives amongst the bodies of civilians executed and dumped in the Quweiq River on March 11.  A Free Syrian Army fighter looks back as smoke rises during fighting between rebel fighters and forces loyal to Syria's President Bashar al-Assad on the outskirts of Aleppo on Saturday, March 2.  Residents read Shaam News newspapers published by the Free Syrian Army in Aleppo on March 2.  A member of the Free Syrian Army reacts to the death of a comrade who was killed in fighting, at Bustan al Qasr cemetery in Aleppo on Friday, March 1.  A rebel fighter throws a home-made grenade at Syrian government forces in Aleppo on February 16.  A member of the Free Syrian Army stands with his weapon as he looks at a rainbow in Aleppo on February 16.  A Syrian woman looks through a bus window in Aleppo on February 14.  Free Syrian Army fighters walk through a dust-filled stairwell in Damascus on February 7.  A Syrian rebel gestures at comrades from inside a broken armored personnel carrier in Al-Yaqubia on February 6.  A rebel fighter throws a hand grenade inside a Syrian Army base in Damascus on February 3.  People stand in the dust of a building destroyed in an airstrike in Aleppo, Syria on February 3.  Free Syrian Army fighters run as they enter a Syrian Army base during heavy fighting in the Arabeen neighborhood of Damascus on February 3.  An unexploded mortar shell fired by the Syrian Army sits lodged in the ground in Damascus on January 25.  Fighters from Fateh al Sham unit of the Free Syrian Army fire on Syrian Army soldiers at a check point in Damascus on January 20.  A Free Syrian Army fighter walks between buildings damaged during Syrian Air Force strikes in Damascus on January 19.  A Syrian rebel fighter tries to locate a government jet fighter in Aleppo on January 18.  Syrian rebels launch a missile near the Abu Baker brigade in Albab on January 16.  A Syrian boy walks near rubbish next to tents at a refugee camp near the northern city of Azaz on the Syria-Turkey border, on January 8.  Syrians look for survivors amid the rubble of a building targeted by a missile in Aleppo on January 7.  A father reacts after hearing of a shelling by forces loyal to Syria's President Bashar al-Assad in Aleppo on January 3.  A patient smokes a cigarette at Dar Al-Ajaza psychiatric hospital in Aleppo on December 18, 2012. The psychiatric ward, housing around 60 patients, has lacked the means to function properly since fighting broke out there in July.  Syrians mourn a fallen rebel fighter at a rebel base in the al-Fardos area of Aleppo on December 8.  Members of Liwa (Brigade) Salahadin, a Kurdish military unit fighting alongside rebel fighters, monitor the area in the besieged district of Karmel al-Jabl in Aleppo on December 6.  A member of Liwa Salahadin aims at a regime fighter in the besieged district of Karmel al-Jabl in Aleppo on December 6.  Two young boys sit underneath a washline in a refugee camp on the border between Syria and Turkey near Azaz on December 5.  The bodies of three children, who were allegedly killed in a mortar shell attack that landed close to a bakery in Aleppo, on December 2, are laid out for identification by family members at a makeshift hospital at an undisclosed location of the city.  Smoke rises in the Hanano and Bustan al-Basha districts in Aleppo on December 1 as fighting continues through the night.  Damaged houses in Aleppo are seen after an airstrike on November 29.  A Syrian rebel mourns the death of a comrade in Maraat al-Numan on November 20.  Syrians protesters stand on Assad's portrait during an anti-regime demonstration in Aleppo on November 16.  A Syrian rebel takes cover during fighting against Syrian government forces in Aleppo on November 15.  Syrian opposition fighter Bazel Araj, 19, sleeps next to his pistol in Aleppo on November 11.  A rebel fighter fires at a Syrian government position in Aleppo on November 6.  A Syrian rebel leaps over debris left in the street while running across a "sniper alley" near the Salahudeen district in Aleppo on November 4.  Rebels hold their position in the midst of a battle on November 3 in Aleppo.  A man cries while being treated in a local hospital in a rebel-controlled area of Aleppo on October 31.  A man is treated for wounds after a government jet attacked the Karm al-Aser neighborhood in eastern Aleppo on October 31.  A Syrian rebel interrogates a handcuffed and blindfolded man suspected of being a pro-regime militiaman in Aleppo on October 26.  Smoke rises from a fuel station following a mortar attack as Syrian women walk on a rainy day in the Arqub neighborhood of Aleppo on October 25.  A Syrian rebel fires at an army position in the Karm al-Jabal district of Aleppo on October 22.  A wounded Syrian boy sits on the back of a truck carrying victims and wounded people to a hospital following an attack by regime forces in Aleppo on October 21.  A man lies on the ground after being shot by a sniper for a second time as he waits to be rescued by members of the Al-Baraa Bin Malek Battalion, part of the Free Syria Army's Al-Fatah brigade, in Aleppo on October 20.  Syrian army soldiers run for cover during clashes with rebel fighters at Karam al-Jabal neighborhood of Aleppo on October 20.  Sm |
