The technology includes increased numbers of Iranian-made surveillance drones and, in some areas, anti-mortar systems similar to those used by U.S. forces to trace the source of mortar fire, the officials and experts said. Syrian military units also are making greater use of monitoring equipment to gather intelligence about rebel positions and jamming devices to block rebel communications, they said.

At the same time, Syrian military leaders are adopting new tactics that some experts also attribute to foreign advisers and training.

“We’re seeing a turning point in the past couple of months, and it has a lot to do with the quality and type of weapons and other systems coming from Iran and Russia,” said a Middle Eastern intelligence official whose government closely monitors the fighting. The official, who spoke on the condition that his name and nationality be withheld in discussing sensitive intelligence, said the new gear is cementing an advantage gained by Syrian forces with the arrival of hundreds of Hezbollah fighters from Lebanon in recent weeks.