Iraqi forces backed by U.S. advisors have launched a new offensive to wrest the western part of Mosul from the hands of the Islamic State.

Iraqi Prime Minister Haider al-Abadi announced that the attack had begun, calling on his forces to respect the human rights of imperiled Iraqis living in the western half of the city. Civilians there are already suffering greatly, as basic needs such as food, water, and fuel are in short supply. Officials fear hundreds of thousands could be displaced.

The fight for Mosul, Iraq's second-largest city, has already slogged on for three months as Iraqi troops encounter stubborn resistance from Islamic State fighters defending their last major stronghold in Iraq. Taking the Western half of the city, which is heavily populated, is not expected to be an easy task for the Iraqi government.

"Mosul would be a tough fight for any army in the world, and the Iraqi forces have risen to the challenge," said Lt. Gen. Stephen Townsend, commander of Combined Joint Task Force Operation Inherent Resolve.