ISIS may face its most serious military challenge — a squeeze on two fronts in the coming weeks from the east and the west. After almost two years of controlling the city of Mosul in Nineveh province, ISIS faces a grim prospect of encirclement and destruction if the combined Iraq-US offensive launched today succeeds in its initial missions. So far, as the Associated Press reports, the liberators have the momentum:

The Iraqi military backed by U.S.-led coalition aircraft on Thursday launched a long-awaited operation to recapture the northern city of Mosul from Islamic State militants, a military spokesman said.

In the push, Iraqi forces retook several villages on the outskirts of the town of Makhmour, east of Mosul, early in the morning on Thursday and hoisted the Iraqi flag there, according to the spokesman for the Joint Military Command, Brig. Gen. Yahya Rasool.

It was not immediately clear how long such a complex and taxing offensive would take. Only recently, Iraqi and U.S. officials refrained to give a specific time on when the Mosul operation could begin, saying it would take many months to prepare Iraq’s still struggling military for the long-anticipated task of retaking the key city.

Now we know why the US has 5,000 troops in Iraq, although we still haven’t gotten any good answers as to why we didn’t put them there two years ago, or leave them in place five years ago. Marines have apparently been softening up these ISIS positions for weeks with artillery support in advance of this operation. It’s hardly been a secret that the next major operation had to wrest Mosul back from ISIS, but it has been a long time coming — and it might be a long time still. The AP notes that sources in both the Iraqi and US military aren’t sure that Mosul can be taken within this year — promising a long, bloody, and house-to-house battle of the kind the US conducted in Fallujah and Ramadi years ago.

On ISIS’ western front, Bashar al-Assad’s forces have recovered enough during the cease-fire of its civil war to enter Palmyra, which fell last year in what was considered “a strategic disaster” for the anti-ISIS coalition:

Syrian government forces have entered the ancient town of Palmyra seized by Islamic State (IS) militants last year, state TV has said.

However, a monitoring group said the fighting was still outside the city, Reuters news agency reports.

Officials launched an offensive to retake the city earlier this month, backed by Russian air strikes.

The Syrians claim to have captured the hotel district in western Palmyra. That has not yet been confirmed independently, but the two actions will tax ISIS’ capabilities. It might have them thinking twice about their war against Europe, especially as fighters become more scarce on both fronts. That is precisely why a forward strategy is necessary to defeat terror networks, and why a ground war is necessary to kill off a terror network that holds significant territory. At the very least, it forces terrorists to pit their strength against military units prepared to fight, rather than civilians in cities far from battlefields unprepared for attacks.

The recapture of both cities will be a welcome development in the war against ISIS, but neither city will ever be the same. The ancient ruins of Palmyra, of such archeological and historical import, have been destroyed forever. In Mosul, an ancient Assyrian Christian culture has been demolished after two millennia of existence, and it seems unlikely that it will return to its previous status even after liberation. We have allowed ISIS to commit genocides and destroy our shared cultural heritage, and that will be a stain on the West for millennia to come.