ISIS snipers, relentless gunfire and mortar shelling are still keeping troops from penetrating the city's border.
CNN Senior International Correspondent Arwa Damon, traveling with US-trained Iraqi counterterrorism forces, was just 200 meters (219 yards) from Mosul's eastern perimeter on Wednesday, with just a barren berm between her and more than 1 million civilians trapped in the city.
"There is no escape route. There have been no routes that anyone has established in fact for the civilian population to leave," she said.
"If the people inside Mosul were to try to make a run for it, they're also risking their lives trying to save themselves."
ISIS has controlled Mosul for more than two years, imposing its own brutal version of Islamic sharia law, responding to "offenses" such as smoking and shaving beards with medieval-style punishments.
Iraqi forces were trying to clear the road to the key city, having freed dozens of villages along the way. They were firing guns at improvised explosive devices (IEDs) and anyone considered a "suspect" as they moved slowly down the road.
Another CNN journalist heard an Iraqi commander tell his unit: "Deal with any civilian as an enemy until we know otherwise." People who are proven not to be "hostile" can take cover inside a nearby mosque, he said.
Forces were using an armored bulldozer to clear trucks and boulders placed by ISIS on the road to slow the troops' advance.
Civilians living on the outskirts of Mosul told CNN that ISIS fighters who lived in their village just days ago have fled into the city. Some fighters have gone to join the fight, while witnesses say some others and their families have been seen on buses, heading for the city's west and, most likely, to Syria.
Officials have warned that entering Mosul will likely trigger the fiercest fighting seen yet in the offensive, and with it a major challenge -- differentiating fighters from civilians.
ISIS is believed to have readied thousands of people to be used as human shields in the city,
making targeted strikes incredibly complicated. Civilians have been advised to hunker down in their homes during the operation.
Army Lt. Gen. Stephen Townsend, who leads the US military in Iraq, including those members advising on Mosul, told CNN that the fight will get more difficult.
"I think it's going to be tougher before it's easier," he told Michael Holmes.
Still, the offensive has played out much like officials anticipated and the Iraqi forces are "doing it their way."
"They have had a pretty challenging fight so far -- and pretty much the fight we thought the enemy would put on," Townsend said.
Iraq-Turkey tensions mount
The village of Gogjali, where Iraqi forces faced heavy clashes with ISIS fighters on Monday and Tuesday, is now about 75% destroyed, according to a CNN estimate.
About 100,000 forces in an Iraqi-led coalition have taken part in a decisive push toward Mosul, freeing communities from ISIS control, village by village. US defense officials estimate that ISIS has about 5,000 fighters in and around Mosul.
The Iraqi-led coalition is an extraordinary union of forces from various religious and ethnic backgrounds that have often stood on opposing sides of the country's history. Among them are Kurdish and minority Shia paramilitary groups, who are still pushing in from the north and south. US special forces have supported the operation.
But only Iraqi forces are entering Mosul, commanders say, a testament to Prime Minister Haider al-Abadi's claims that the battle for the city is at its core an Iraqi fight, and that sectarian politics must be kept from the battle.
Tensions, however, are flaring with Turkey
, which moved tanks and bulldozers to its border at the closest point to Mosul on Tuesday, saying only that it was to deal with "terrorism."
Iraq has warned Turkey it is not welcome to take part in the offensive. But Ankara says it has already taken part in an assault, on the request of Kurdish Peshmerga forces that Turkey has trained.