BEIRUT (AP) -- The instances in which chemical weapons are alleged to have been used in Syria were purportedly small in scale: nothing along the lines of Saddam Hussein's 1988 attack in Kurdish Iraq that killed thousands.
That raises the question of who would stand to gain as President Bashar Assad's regime and the opposition trade blame for the alleged attacks, and proof remains elusive.
Analysts say the answer could lie in the past -- the regime has a pattern of gradually introducing a weapon to the conflict to test the international community's response.
The U.S. said last week that intelligence indicates the Syrian military has likely used sarin, a deadly nerve agent, on at least two occasions in the civil war, echoing similar assessments from Israel, France and Britain. Syria's rebels accuse the regime of firing chemical weapons on at least four occasions, while the government denies the charges and says opposition fighters have used chemical agents in a bid to frame it.
But using chemical weapons to try to force foreign intervention would be a huge gamble for the opposition, and one that could easily backfire. It would undoubtedly taint the rebellion in the eyes of the international community and seriously strain its credibility.
Mustafa Alani, an analyst at the Gulf Research Center in Geneva, said it would also be difficult for the rebels to successfully employ chemical agents.
"It's very difficult to weaponize chemical weapons," he said. "It needs a special warhead, for the artillery a special fuse."
In the chaos of Syria's civil war, pinning down definitive proof on the alleged use of weapons of mass destruction is a tricky task with high stakes. President Barack Obama has said any use of chemical arms -- or the transfer of stockpiles to terrorists -- would cross a "red line" and carry "enormous consequences."
Already, the White House's announcement that the Syrian regime appears to have used chemical arms has ratcheted up the pressure on Obama to move forcefully. He has sought to temper expectations of a quick U.S. response, saying too little is known about the alleged attacks to take action now.
Analysts suggest that a limited introduction of the weapons, with little ostensible military gain, could be an attempt by the Syrian government to test the West's resolve while retaining the veil of plausible deniability. This approach would also allow foreign powers eager to avoid a costly intervention in Syria to remain on the sidelines, while at the same time opening the door for the regime to use the weapons down the road.
"If it's testing the water, and we're going to turn a blind eye, it could be used widely, repeatedly," Alani said. "If you are silent once, you will be silent twice."
The slow introduction of a weapon to gauge the West's response fits a pattern of behavior the Assad regime has demonstrated since the uprising began in March 2011, according to Joseph Holliday, a Syria analyst at the Washington-based Institute for the Study of War.
When largely peaceful protesters initially took to the streets, the regime responded with small arms fire and a wave of arrests. As the government ramped up its violent crackdown, the opposition began to take up arms in late 2011, prompting yet another escalation in force by the regime.
In early 2012, government troops began using heavy weapons, first in a relatively restrained manner on military targets.
"Once they could confirm that there wasn't going to be a major reaction from the West, they were able to expand the use of artillery," Holliday said.
By the summer of 2012, government troops were pounding rebellious neighborhoods with tank fire, field cannons and mortars, but the rebellion was stronger than ever, prompting Assad to turn to his air force, and the regime's MiG fighter jets and helicopter gunships began to strike military targets in rural areas.
After the government was satisfied that the international community wasn't going to impose a no-fly zone like NATO did in Libya, Assad unleashed the full might of his air power, and warplanes have been indiscriminately bombing rebel-held areas since.
"It all fits the pattern of being able to do this incrementally," Holliday said.
"It's been important for the regime to introduce these capabilities as gradually as possible so that they don't trip the international community's red lines," he added. "I think this is basically a modus operandi that the Assad regime has established and tested with the United States, and confirmed that it works, and he's using it again with chemical weapons."