Iraqi forces are poised to launch an all-out assault on one of the last major Islamic State strongholds in the face of a counter-attack by the extremists.
The fighting around Fallujah, which lies around 40 miles west of the capital Baghdad, has led to a fresh exodus of fleeing civilians amid concern for an estimated 50,000 people, who remain trapped.
The troop build up has now been completed ahead of a planned final push into the city centre.
It comes as the army sought to tighten its grip on the region, having claimed to have already recaptured 80% of the territory around Fallujah.
In response, IS attacked the town of Heet, around 85 miles west of Baghdad, which was recaptured by the army just last month.
However, the military said the assault had been "thwarted", with coalition aircraft targeting the militant forces.
The jihadists also launched an offensive in northern Syria against the towns of Marea and Azaz.
Iraq commanders have declined to comment on troop numbers or the timing of the expected assault on Fallujah.
But soldier Ali al Shimmari said: "I'm totally ready for it. I phoned my family in the morning and asked them to pray for me to get back safe to them," he added. "I'm determined to end Daesh."
Nasr Muflahi, Iraq director of the Norwegian Refugee Council, said: "We are receiving hundreds of displaced Iraqis from the outskirts of Fallujah who are totally exhausted, afraid and hungry."
Fallujah saw some of the heaviest fighting of the 2003-2011 US-led military invasion.
In January, 2014, it was also the first Iraqi city to fall to IS - six months before the extremists swept across northern and western Iraq and declared a caliphate.
