Complex sentence: The overhead fire sprinklers were immediately turned on, but the fire could not be extinguished for nearly an hour, not least because the electric motors driving the steel fire curtains had been damaged in the first kamikaze attack and could only be repaired by a dockyard.
Split into simpler sentences: The overhead fire sprinklers were immediately turned on, but the fire could not be extinguished for nearly an hour. Not least because the electric motors driving the steel fire curtains had been damaged in the first kamikaze attack and could only be repaired by a dockyard.