Complex sentence: The Mayor of Saumur was not sure they wanted to be defended, all towns with a population of over 20,000 had been declared open, Saumur now full of refugees possibly qualified but the army would not countenance making the town open or allowing the population to evacuate.
Split into simpler sentences: The Mayor of Saumur was not sure they wanted to be defended; all towns with a population of over 20,000 had been declared open. Saumur, now full of refugees, possibly qualified, but the army would not countenance making the town open or allowing the population to evacuate.