BAGHDAD — On land, Syria’s government is mustering thousands of conscripts to bolster its depleted forces. At sea, a Russian naval flotilla is just offshore, ready to intervene with formidable firepower. In Idlib Province, millions of civilians are dreading what comes next.

The warring sides in Syria’s long and merciless civil war are preparing for another brutal offensive, and this one may be the last.

The looming assault on Idlib Province is the one the government in Damascus hopes will deliver the final military blow against the rebel fighters and their civilian supporters who rose up more than seven years ago demanding regime change.

Where Syria and its Russian and Iranian allies see a chance to crush the remaining opposition, Western leaders warn of a humanitarian calamity in Idlib, where an estimated three million civilians live.