As Mosul has fallen, neighborhood by neighborhood, to government forces, Daesh has responded by retreating with their families to a smaller and smaller area of the city. This is documented. Civilians who have no connection to Daesh have already left and the civilians in the last, surrounded area of the city are essentially ISIS supporters. 
They have an option. They can surrender. Their position is untenable. Leaflets have been dropped into the area telling them this. By continuing to fight when their position is indefensible they are essentially condemning themselves and their families to death. 
But it is their choice. Daesh will fall one way or the other.