The outgoing American commander of coalition forces battling the Islamic State in Iraq and Syria gave an upbeat assessment of the progress of the war Wednesday, saying the coalition has killed an estimated 45,000 Islamic State fighters, and retaken 25,000 square kilometers of Islamic State-held territory.

Army Lt. Gen. Sean MacFarland said the tide of battle turned with the fall of Ramadi last year, and predicted the inevitable liberation of Mosul will leave only scattered remnants of Islamic State fighters in Iraq.

When MacFarland assumed command last September, the war against the Islamic State was essentially stalled, with Syrian opposition forces "hanging on along the Mara line by their fingertips in northwest Syria.

"You don't hear the word 'stalemate' anymore," MacFarland told reporters at the Pentagon via teleconference from the region, marking two years of coalition actions against the Islamic State.

MacFarland said in retrospect, the turning point came with the liberation of Ramadi by Iraqi forces last year, just as it was a turning point for U.S. troops in 2006 during Operation Iraqi Freedom.

"To paraphrase Winston Churchill," MacFarland said, "the liberation of Ramadi was the end of the beginning of the campaign against Daesh [the Islamic State]. The beginning of the end will be the liberation of Mosul, Iraq's second-largest city. Once it is recaptured, the enemy in Iraq will be reduced to scattered pockets of resistance."

MacFarland refused to put a timeline on the long-awaited Mosul offensive, but he did predict that in Syria, U.S.-backed opposition fighters will retake Manbij within weeks or maybe sooner.

He called Manbij an important objective for both sides, noting there are a lot of foreign fighters, and they haven't cut and run.

He predicted when it falls to opposition forces it will be "one more nail in the enemy's coffin."