The whole concept of the board game is used in about a 5-minute window in the movie when Hopper and his new friend Nagata look for traces of the alien ships by disturbed buoys in the water. They can track the alien warships' paths, and torpedo the first two with little resistance - but the third one is onto their plan and chases them around the island.
They wait for their moment when the sun will beam directly into the alien cockpit, then use sniper rifles to break the glass and strike them down.
Sam and the disabled veteran on the island get a message to Hopper that the island is being used by the bad guys to set up a communications array, and to take it out.
They crew don't get that far, and the battleship is torn apart by two of the laser-powered grinding machines.
They limp to shore and board the only battleship remaining - the USS Missouri docked museum. Hopper inspires the aged crew, and all the nationalities and generations work together to get it moving again.
Meanwhile, the mothership emerges from the water, not too happy that the little jet-ski versions have been taken out and targets the Missouri. Just before it fires, Hopper drops the anchor, swings around, and launches a broadside on the enemy. It then releases the anchor, surging forward and away from more missiles (which are meant to look like Battleship game pegs), and fires some more.
The good guys are hanging on, and keep trading blows. Finally the mothership starts to give and the huge force-field evaporates.
Admiral Shane sends in the planes to help Hopper.
The Mothership is going down, but launches a few more grinders at the Missouri. The crew look on helpless - just as jet fighters do a fly-by and blow them from the sky.
With only one shell left, the Missouri crew heave the casing through the ship before they launch it at the island's communication array to save the day.
At the end, the commanders are awarded at a large ceremony, and Hopper's brother is awarded posthumously. Hopper himself is awarded with one of the highest honours for his bravery.
He summons up the courage and asks Admiral Shane for his daughter's hand in marriage - but Shane refuses. He then mentions something about a chicken burrito. Hopper gets the joke and follows him for a drink, now the best of friends.