Roger and Maurice are the ones that attack Jack and Piggy because Jack wants Piggy's glasses.
After Jack leaves to go to Castle Rock, Piggy becomes more confident with himself, and starts to stand up for himself. This happens because Jack stole Piggy's glasses, and now he can no longer hide behind his disability of not being able to see.
Piggy
Piggy and Jack are complete opposites so they were bound to but heads. In the beginning Jack and Piggy didn't have a problem with each other but as the story progressed the more Jack hated Piggy. It never really stated why they don't get along but I think that it's because Jack has a different personality. Jack is power thrived while Piggy is more intellectual. Hope that helped!
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.
Jack took Piggy's glasses.
Jack and his followers steal piggy's glasses.
Roger and Maurice are the ones that attack Jack and Piggy because Jack wants Piggy's glasses.
piggy's glasses
After Jack leaves to go to Castle Rock, Piggy becomes more confident with himself, and starts to stand up for himself. This happens because Jack stole Piggy's glasses, and now he can no longer hide behind his disability of not being able to see.
Piggy
Jack initially dismisses Piggy and the influence he has on the group. He belittles Piggy's intelligence and continually undermines his authority in order to maintain control over the other boys on the island. Eventually, Jack's treatment of Piggy escalates into physical violence, culminating in Piggy's tragic death.
When Jack said he didn't hunt, Piggy mocked him by saying that Jack couldn't hunt as he was just a boss. Piggy implied that Jack was incompetent and only good at giving orders, not actually participating in the hunting.
Jack orders the boys to kill Piggy and Ralf.
Both Jack and Piggy, are stubborn English boys of about 12 years old and symbolically represent groups of society and parts of the human thought, but Jack and Piggy's similarities end there
Jack and his tribe.
Piggy's glasses