Complex sentence: For four long winter months, William Shirley, who had ordered their deportation, had not allowed to them disembark and as a result, half died of cold and starvation aboard the ships.
Split into simpler sentences: For four long winter months, they were not allowed to disembark on orders of the one who had given orders to deport them, William Shirley. As consequence, half died of cold and starvation aboard the ships.