Complex sentence: As fighting took place in the streets of the town, the citizens would have been caught up in the fighting and because the battle took place at night and in heavy rain, it would have been difficult to distinguish between citizens and armed combatants.
Split into simpler sentences: As fighting took place in the streets of the town, the citizens would have been caught up in the fighting. Because the battle took place at night and in heavy rain, it would have been difficult to distinguish between citizens and armed combatants.