What finally saves Ralph from jacks and his hunters?

Fleeing from Jack and his hunters Ralph stumbled onto the beach, near the shelters, and was confronted by a naval officer. Jack and his hunters also emerged from the jungle a short distance behind Ralph but immediately stopped their pursuit of Ralph on sighting the officer. You might therefore say that the arrival of the officer saved Ralph from Jack and his hunters. However the officer was only there because his ship had sighted the smoke coming from the island. The smoke came from the out of control fire which Jack had lit to try and drive Ralph from his hiding place. So, with typical Golding irony the fire which Jack lit in an effort to kill Ralph proved to be Ralph's salvation.