Complex sentence: The Lastekodumägi fell entirely to the Soviets, with the 191st Rifle Regiment at the head of the Soviet attack suffering great casualties in the fire of the last defenders of the hill who were killed or forced to the next hill, the Grenaderimägi.
Split into simpler sentences: The Lastekodumägi fell entirely to the Soviets with the 191st Rifle Regiment at the head of the Soviet attack. These suffered great casualties in the fire of the last defenders who in turn were either killed or forced to the next hill the Grenaderimägi.