The battle for the last scrap of land held by the Islamic State of Iraq and Syria (ISIS) in Syria has taken longer than expected, with the terror group vowing to fight to the last man in Baghouz. In the shadow of moonlight alone, U.S.-backed forces took CBS News to the closest point yet overlooking the last of ISIS. Soon after, you could hear bullets whizzing overhead.

For weeks, U.S. and coalition airstrikes have been battering a tiny area now down to just a few hundred square yards. Yet on Monday, soldiers of the Syrian Democratic Forces were locked in a firefight with ISIS militants who continue to survive the onslaught.

On a hilltop within the sites of ISIS snipers, a lone SDF gunner took aim at targets down below. The so-called caliphate has been reduced to a junkyard, a tangled maze of wrecked vehicles surrounded on all sides.

While it's unclear how many ISIS fighters remain, it's enough to put up a fight. Human shields have been the biggest hurdle. An estimated 1,500 people at first turned out to be closer to 30,000.

Yet that is not enough to explain how ISIS has made a last stand that has withstood the might of the most powerful military in the world and its allies here on the ground for so long.

Commanders have quit trying to predict when this fight might be over. When CBS News first got to Syria, they said ISIS would be finished in a matter of days. That was more than two months ago.