Complex sentence: They saw the theater as the most likely place where the Ottoman Empire might be eliminated from the war, resulting in the isolation of the German Empire, and freeing British Empire forces then serving in Mesopotamia and Palestine, for transfer to France.
Split into simpler sentences: They saw the theater as the most likely place where the Ottoman Empire might be eliminated from the war. This would isolate the German Empire, and make British Empire forces, then serving in Mesopotamia and Palestine, available for transfer to France.