Complex sentence: Efforts to destroy the guns by aerial bombing have proved fruitless, so that six destroyers can pick up the stranded men, Commodore Jensen (James Robertson Justice) of Allied Intelligence gathers a team of commandos to sail to Navarone and destroy the guns.
Split into simpler sentences: Efforts to destroy the guns by aerial bombing have proved fruitless. So that six destroyers can pick up the stranded men, Commodore Jensen (James Robertson Justice) of Allied Intelligence gathers a team of commandos to sail to Navarone and destroy the guns.