Imagine the population of Birmingham is made homeless. One million people suddenly facing a life on the road with nowhere to go, no food, no shelter.
How would the UK cope? Even a nation living without war and in relative wealth would struggle to accommodate the needs of so many people. What would you do? Where would you go?
This is not purely a hypothetical question - it is the current reality facing Mosul's embattled residents.
In the coming days up to one million people are expected to flee their homes as the military operation increases fighting in and around Mosul. This is in addition to the three million people already displaced by this conflict, and the 10million Iraqis across the country in need of aid.
As the fighting has intensified, preparations have been taking place. Military supplies have been positioned and journalists dispatched to cover the story.
For aid agencies the big question has not only been when, but also how. How do you help one million people who need food, water and shelter and mobilise that amount of aid in such a short window of time? Communities across Iraq have already taken in millions of displaced people, but even with the greatest will they cannot spontaneously accommodate a million more. After the basics of food, water and shelter are met, how many temporary medical facilities might be needed, how many doctors? What psychological needs will people have?
Setting up camps at short notice requires huge amounts of organisation. Essential elements like sanitation must be taken into account in both camps and public buildings being used as shelters, otherwise people who have escaped bullets and bombs could find themselves at risk from waterborne diseases, like typhoid and cholera.
The International Committee of the Red Cross (ICRC) is ready to provide around 800,000 people with food and has teams in areas including Erbil, Dohuk, Kirkuk and Ramadi. Our partner the Iraq Red Crescent has over 2,500 volunteers ready to supply families with clean water, blankets and other essentials such as soap and kitchen sets. Health facilities in the area have received extra supplies and water tanks have been repaired so displaced people have access to clean and safe water.
But we need more than emergency supplies. Over recent weeks and months we've seen attacks on civilian targets such as hospitals and aid convoys in Syria and Yemen. We appeal to all parties to respect the basic principles of international humanitarian law - precaution, protection and distinction of civilians. Everything must be done to allow the safe and unimpeded access to any humanitarian organisation working to protect and assist the people fleeing Mosul.
The Red Cross Red Crescent will be there, but we need you to support us.
You can support the people of Mosul by giving to the British Red Cross Iraq appeal. (www.redcross.org.uk/Iraq)