ISTANBUL — Russia has expanded its role in the Syria conflict and is now by far the dominant power in the air war, according to rebel military commanders and a leading Syrian human rights monitor. Commanders say that as a result even if the U.S. were to knock out the entire Syrian Air Force, that wouldn’t turn the tide of the war.

President Vladimir Putin ordered the Russian military intervention in September 2015 when the Assad regime was said to be on the brink of collapse after rebels captured Idlib province in northern Syria, and since then dependence on Moscow has grown steadily.

Russia’s lead role in the air war is evidenced by the airstrikes against Syrian civilian targets since last Friday, when the U.S. fired 59 cruise missiles at Shayrat, a Syrian airbase in central Homs province. The U.S. government said Shayrat was the launch point for a chemical weapons attack on the town of Khan Sheikhoun in southern Idlib province, in which more than 100 people died, according to local officials.

Over the five days between Friday and Tuesday evening, Russian airstrikes caused the deaths of 56 civilians, including 10 children and eight women, the Syrian Network for Human Rights reported Thursday. Syrian government forces, including foreign militias, killed 42, SNHR said.

On Wednesday and Thursday, Russian warplanes took the lead role in airstrikes in Aleppo, Idlib and Hama provinces, according to opposition media and local officials.

Russia and Syria divided up the task of targeting public buildings and medical facilities. All are protected under international law, making each strike a potential war crime. According to SNHR’s accounting of the first five days. Russian aircraft bombed two mosques, one school and three medical facilities while Syrian aircraft — some of which are now piloted by Russians — attacked two mosques, two schools one medical facility, one market and one civil defense center, SNHR said.

No one has accused Russia of using banned chemical weapons, but U.S. officials say they suspect Russian military officers were aware that the Assad regime was deploying them. Russia had its own forces stationed at the same Shayrat air base.

In fact, according to SNHR, Shayrat was the second most used airbase by Russian warplanes after Hmeimim in Latakia province on the Mediterranean.

In the attacks on civilian targets since Friday, Russia has deployed banned cluster munitions—small bomblets that are intended as an antipersonnel weapon—at least four times, and incendiary weapons in at least six attacks in those five days alone, SNHR said. The Qatar-based SNHR is often cited by the State Department as a source of data on war crimes.

There’s no question that Russia plays the lead role in the air war, according to defected Syrian military officers who track the movements of regime and Russian warplanes in order to warn civilians of impending air strikes.

When there’s heavy fighting in northern Hama and southern Idlib, at least 175 of the 250 warplane movements in the area are Russian and the rest Syrian, Col. Mustafa Bakkour, who heads the warplane tracking operation in North Hama, told The Daily Beast. The numbers include helicopter movements as well as fixed wing, and count aircraft that often stage several attacks on each sortie, he said. Throughout Syria, when there is fighting on several fronts, there can be as many as 500 sorties daily, he said.

“The problem for us isn’t the Syrian Air Force so much as the Russian Air Force,” said Major Muhammad Mansour, commander of the Nasr Army, one of the main rebel groups in north Hama. “It is the Russian warplanes which are shifting the balance in the battle for the regime side.” The Nasr army receives covert U.S. support.

“We have a dire need for air defense weapons to be able to confront the Syrian and Russian warplanes,” Col. Yusuf al Miri’e, the spokesman of the rebel Southern Front said. The Obama administration refused to provide air defense to rebel forces, even those obtaining other forms of military aid through the CIA program.

Moscow’s role in the air war poses a quandary to U.S. military planners hoping to head off another Syrian chemical warfare attack. In an effort to avoid a direct confrontation last Friday, the Pentagon sent a warning to the Russian military, which was able to remove its officers from the Shayrat airbase before the U.S. attack.

The challenge is how to get the message across to President Bashar al Assad, who in an interview Wednesday denied that Syria has ever used chemical weapons and disputed reports that anyone had died in the April 4 gas attack on Khan Sheikhoun.

The White House and the Pentagon earlier this week threatened further retaliation against the Syrian military if it mounts another sophisticate chemical weapons attack or continues dropping barrel bombs, crude weapons sometimes loaded with chlorine, an industrial chemical.

Administration officials said the Syrian army lost 20 per cent of its operational air force in Friday’s missile attack on Shayrat air base.

Noting those losses, Defense Secretary James Mattis warned Monday that the Syrian government would be “ill-advised ever again to use chemical weapons.” White House spokesman Sean Spicer expanded the warning to include continued attacks with barrel bombs against civilians.

“The President has made it very clear that if those actions were to continue, further action will definitely be considered by the United States,” Spicer said.

But Assad is living in a different world. In his interview with the French AFP news agency published Thursday, he also denied that Friday’s U.S. missile attack had caused any damage to his forces. "Our firepower, our ability to attack the terrorists hasn't been affected by this strike,” he claimed.

And while he was most probably rattled by the U.S. intervention, he appears determined to play it down, for domestic consumption at least.

On Friday, some hours after the U.S. missile attack, the Syrian regime used chemical weapons in a military encounter with rebel forces in Qaboun, a neighborhood in east Damascus, according to SNHR. It said regime soldiers threw two hand grenades filled with poison gas into the rebel frontline. The grenades, suspected to contain chlorine gas, caused symptoms bronchial damage, severe coughing and breathing difficulties, SNHR said.

But this is part of a pattern of multiple violations of the Syrian regime’s pledge to abandon all use of chemical weapons. SNHR said it had documented 168 regime chemical attacks since September 2013, when chemical weapons killed more than 1,000 civilians in Mouademiyeh, a Damascus suburb, according to the U.S. government.

The regime also has used barrel bombs in its battle against rebel forces in Dara’a in southern Syria since Friday, as well as in other locations in northern Syria, according to the Local Coordination Committees and opposition media there.

Assad’s denials in the AFP interview put him at direct odds with his Russian backers. Referring of the U.S. government, he said: “They fabricated the whole story in order to have a pretext for the attack.” This reflects, in fact, the line being put out by Iran, which may try to back Assad even if Russia eventually forsakes him.

As for the deaths of the children and the images of victims foaming at the mouth and convulsing, Assad declared: “We don’t know whether those dead children were killed in Khan Sheikhoun. Were they dead at all?”

He said the story of Khan Sheikhoun “is not convincing by any means.”

This contrasts with the statement by Sergei Lavrov, the Russian foreign minister, during an otherwise contentious news conference after talks with U.S. Secretary of State Rex Tillerson on Wednesday. Lavrov referred to the “Idlib incident, where chemical weapons were used, and the subsequent U.S. missile strike on April 7.”

This wasn’t the only time Assad and the Russians were on different wavelengths. The Syrian high military command said Thursday that many people were killed in an airstrike late Wednesday by the U.S.-led coalition attacking an ISIS chemical weapons depot near the east Syrian city of Deir Ezzor. The coalition denied the report, and Maj-Gen. Igor Konashenkov, the spokesman of the Russian Defense Ministry, said he had no information about an airstrike or casualties.