The stockade on the island proves to be an excellent protection and advantage for the others against the pirates because it is a sturdy fortification with only small openings for placing rifles for shooting. In addition, it has water close by. On the other hand, it puts the men at a disadvantage when the pirates shoot the long-nine gun that proves light enough for them to bring ashore.
In Chapter XV, after Captain Smollett and his men lock some of the mutineers under the deck, Captain and Dr. Livesey go ashore to find a spot where they can get fresh water, organize themselves, and prepare for the possible appearance of the pirates on the island. Soon, they find an abandoned stockade near the spot where they have sighted water; therefore, the men go inside with their water. There they set up a defensive position against the pirates on the island that affords them excellent openings for shooting. Jim describes the stockade in this way:
The people in the log house....stood quiet in shelter and shot the others like partridges. All they wanted [meaning needed] was a good watch and food; for, short of a complete surprise, they might have held the place against a regiment.
However, one thing that Captain Smollett and Dr. Livesey have not figured on is the cannon on the ship and, especially, the smaller long-nine gun that the others could even bring ashore. Fortunately, only the flag on the stockade is visible for the men on the ship to aim at as they fire on those inside.