But many of their officers are not as familiar with the terrain and the streets ahead as ISIS fighters, who have had two years to fortify defenses, dig trenches and tunnels and take over abandoned houses.
Add the reduced visibility of a sandstorm, and the odds tipped a little more in favor of the militants. The dust can clog more sophisticated weapons and reduces the effectiveness of thermal imagery.
As an unconventional force substantially outnumbered by its adversaries, ISIS has often taken advantage of nature -- fog, low cloud and sandstorms -- as well as the cover of night. A huge sandstorm around Ramadi helped it penetrate Iraqi forces' defensive lines
in May 2015.
By the time the sandstorm had subsided, the attackers were so intermingled with Iraqi troops that the use of airstrikes was nearly impossible. Days later, the last Iraqi forces were swept from Ramadi.
In the same month a massive sandstorm that covered nearby Fallujah also enabled ISIS to stage several successful suicide attacks.
ISIS also used dense fog in January 2015 to stage a sneak attack on Kurdish Peshmerga positions south of Kirkuk, killing a general and briefly pushing the defenders back toward the city.
Peshmerga fighters on the front lines at that time told CNN that their worst fear was the fog that often came with the dawn on winter mornings.
Back in 2003, the US invasion of Iraq was slowed for several days by a massive sandstorm around Najaf. In a later account of the war, Corporal Zack Brackney recalled everything slowly turning a yellowish-orange color as visibility dropped to 10 meters.
His unit moved only to conduct defensive patrols around their perimeter. Ocher dust invaded every crevice of weapons, clothing and vehicles.
Sandstorms and low visibility can also hinder aerial reconnaissance and especially the use of helicopters. But the most modern fighters and bombers are impervious to the dust clouds below.
US General Tommy Franks said that even in the middle of the 2003 sandstorm, B52s, B-1 bombers and other aircraft were able to target with precision the stationery Iraqi Republican Guard far below.
Iraq ministry believes storm frequency will double
Down the ages, many armies have seen opportunity when sandstorms have kicked up. The ancient Chinese military historian and strategist Sun Tzu quoted an officer named Li Shou-Cheng who was facing a dauntingly superior enemy.
"They are many and we are few, but in the midst of this sandstorm our numbers will not be discernible; victory will go to the strenuous fighter, and the wind will be our best ally."
The chances are that in Iraq sandstorms will increase in frequency and intensity, thanks to drier, hotter summers. The Iraq Ministry of Environment recorded 122 dust storms in 2012
and predicted the number could double within 15 years.
The current southerly winds blowing toward Mosul are expected to ebb in the next couple of days, but there has been no rain in Mosul for months and there's none in the immediate forecast.
The dust and sand may return to hinder the Iraqi army and offer a blanket of cover to ISIS.
In a video released late Tuesday, ISIS fighters were seen celebrating the arrival of the sandstorm, with one exclaiming that God had sent his soldiers to create the sandstorm to confront their enemies.