In Chapter 8 of "Lord of the Flies", Jack and his hunters in face paint, steal fire for Ralph and Piggy.
In William Golding's novel "Lord of the Flies," it is Jack's group of savages who accompany him to steal fire from Ralph's camp. They violently attack Ralph and the other boys to steal the fire and assert their control over the island.
the guy who accompanies jack along with Robert to steal fire from Ralph's group
Maurice and Robert.
They were fighting with Roger, and Jack stole fire from Piggy and Ralph.
Prior to holding a feast on the beach Jack, accompanied by four hunters visited Ralph's group at the shelters. Two unnamed hunters grabbed burning braches and ran off along the beach with them. Jack, flanked by Maurice and Robert, delivered a speech inviting the rest of the boys to his feast. Later in the book Jack selected Roger and Maurice to accompany him on his raid to 'get fire' from Ralph's group, infact they stole Piggy's glasses.
Roger accompanies Ralph and Jack up the burned part of the mountain.
There is no attack by Jack's tribe on Ralph and his followers. Jack led a night-time raiding party, comprising of himself, Roger and Maurice, to steal Piggy's glasses in chapter 10: The Shell and the Glasses.
Well in chapter 10 Jack and his tribe of savages invade Ralph's tribe (made of up Ralph, Sam and Eric, Piggy, and one/two littluns) in order to steal Piggy's glasses, which is overall the power to start a fire on the island. Jack might have mentioned this plan in chapter 9 so I'm hoping this is the right answer to your question.
Ralph opposes Jack's violent ways. He also trying to stop the boys approaching Jack's view of the boys. Moreover, by hunting Ralph, Jack is trying to show who the real leader is and why everyone should follow him.
jack starts the fire to get ralph out of his hiding
Jack's boys do not attack Ralph's boys at any point in the book. Roger and Maurice accompany Jack on a night time raid on the shelters but the purpose is not 'attack' anyone but simply to steal Piggy's glasses. Even when Ralph, Samneric & Piggy go to castle rock to demand the return of Piggy's glass although they are vastly outnumbered by Jack's tribe they are not attacked.
Jack Divides His Group Group Into Two, Which Are The Ones Who Maintain The Cave And Keep It From Intruders And Followed BY The Hunters Who Basically Hunt And Steal Fire From Ralph's Group.
It was Jack's job to maintain the fire, but he was hunting instead. Ralph is mad because while Jack was hunting the fire went out and a ship went by. If Jack had maintained the fire they might have been rescued.