Complex sentence: The expedition attempted to return, but the weather turned against them and they were stranded in the region for the next four years, until rescued in 1917 by the ship "Neptune", commanded by Captain Robert Bartlett.
Split into simpler sentences: The expedition attempted to return, but the weather turned against them and they were stranded in the region for the next four years. They were eventually rescued in 1917 by the ship "Neptune", commanded by Captain Robert Bartlett.