Dozens of defense and foreign ministers will meet in Washington on Wednesday and Thursday to take stock of the fight against Daesh (the so-called IS), their focus increasingly on a major prize: the militant group's bastion in Mosul, Iraq. The battle for Mosul is expected to be difficult, but the aftermath could be tougher, Iraqi, United Nations and US officials say. Plans are still being finalized to provide urgent humanitarian aid and restore basic services and security for residents and as many as 2.4 million displaced people. Defense ministers of the anti-Daesh coalition will meet at Joint Base Andrews outside Washington, followed by a joint session of foreign and defense chiefs on Thursday. The United Nations is preparing for what it says will be the largest humanitarian relief operation so far this year as terrified people stream out of the path of the advancing Iraqi military and flee from the city itself. They will need shelter, food and water, and sanitation for three to 12 months, depending on the extent of the city's destruction. "There is a logic in moving as quickly as possible, but there is a danger that if the humanitarian response is not as prepared ... then we could have a humanitarian catastrophe and possible problems with political management of Mosul after its liberation," said a senior diplomat based in Baghdad, speaking on condition of anonymity. The vast majority of the expected refugees will be Sunni Muslims, many of whom feel disenfranchised by Iraq's Shiite-led government in Baghdad, and that presents what could be an even bigger problem. "Unless underpinning an offensive on Mosul are real political settlements between the Sunnis and the Shiites, we think it's only a matter of time before it unravels again," said a source in the Kurdish regional security council. Iraqi Prime Minister Haider Al-Abadi plans to install a military governor for Mosul after Islamic State is expelled, several sources said. Comustible mixture Mosul, which Daesh seized from a collapsing Iraqi army in June 2014, is Iraq's second biggest city and home to a combustible mixture of Sunni Arabs, Kurds, Turkmen and others. Although Iraqi and US officials have not announced a timetable for moving on the city, a senior Baghdad-based diplomat said Prime Minister Abadi wants to advance the start of the Mosul campaign to October after the seizure of the city of Falluja from Daesh last month. This month, Iraqi forces backed by US air power retook Qayara air base south of Mosul, which will be turned into a logistics hub for the main assault on the city. "We're looking ahead to Mosul, which will be the most significant challenge yet," Brett McGurk, US President Barack Obama's special envoy in the fight against Daesh, said on Tuesday. McGurk said he met recently with Iraqi officials in Erbil to discuss the "disposition of forces" for the battle. Troops will include Kurdish peshmerga fighters, the Iraqi military and 15,000 local fighters from Nineveh province, he said. McGurk described three other challenges this week's meetings will address in detail: plans for immediate humanitarian relief; short-term stabilization of Mosul; and local governance. When asked whether he thought Daesh would put up a strong fight in Mosul, Iraqi foreign minister Ibrahim Al-Jaafar said he expected them to behave as they did in Falluja "In Falluja they threatened and vowed to fight until the last breath ... issues ended differently; some were killed, some were defeated early and some disguised as women to flee," Jaafari said in Washington.