Complex sentence: As the towering cloud of smoke collapsed back onto the convoy, several ships closed on the Burke's former position to search for survivors, though it was soon clear that the SS John Burke, and all 68 men aboard her, were gone.
Split into simpler sentences: As the towering cloud of smoke collapsed, several ships closed on the Burke's former position to search for survivors. It was soon clear that the SS John Burke, and all 68 men aboard her, were gone.