Complex sentence: The acrimony between the British and French caused by these actions escalated when the British attempted to repatriate the captured French sailors: the British hospital ship that was carrying them back to France was sunk by the Germans, and the French blamed the British for the deaths.
Split into simpler sentences: The acrimony between the British and French caused by these actions escalated when the British attempted to repatriate the captured French sailors. The British hospital ship that was carrying them back to France was sunk by the Germans, so the French blamed the British for the deaths.