In the Islamic State-held city of Mosul, snipers, landmines, hunger and thirst await those attempting to leave.
Staying, however, keeps them in the snare of the militant group, notorious for using civilians as shields in battle.
Either way, Mosul residents are trapped, and the campaign to retake the city could drag on for months.
The UN's Office for the Coordination of Humanitarian Affairs predicts the humanitarian operation in Mosul could be the world's largest and most complex of 2016.
By UN estimates, the military campaign is expected to impact the city's entire population of approximately one.five million.
About 200-thousand people are expected to flee their homes in the first weeks of the campaign, but only 60-thousand can be accommodated in the emergency tent camps set up in areas nearby.
At least 250-thousand more tents are under construction or planned.
In addition, Reuters reported Tuesday the U.S. expects ISIS to use chemical weapons in the course of the offensive.
More than 98-thousand people -- including U.S. soldiers and Iraqi security forces -- are engaged in the fight against approximately five-thousand ISIS fighters.
U.S. President Barack Obama on Tuesday acknowledged there is a "difficult fight" ahead, but asserted that the coalition will ultimately be successful.
The International Organization for Migration says the aid effort could cost an estimated 347 million U.S. dollars, but that only half of that amount has been raised so far.
Meanwhile, Julian King, the EU Commissioner for the Security Union, has urged European countries to prepare for returning jihadists, if the Islamic State is driven out of Mosul.
Speaking to a German newspaper on Tuesday, he said Europe must boost its border defense and increase its resilience to terrorism, stressing the threat posed by even a small number of ISIS members returning to Europe could be "very serious."
Raffaello Pantucci, the director of International Security Studies at the Royal United Service Institute, warned that ISIS has shown a capacity to send fighters back hidden among refugees entering Europe.
Hwang Hojun, Arirang News.