Jack steals Piggy's glasses because he sees them as a valuable resource needed for making fire, which he believes will help him gain power and control over the group. In his pursuit of dominance, he disregards Piggy and the consequences of his actions.
to build his own fire
Jack and his followers steal piggy's glasses.
Piggy's glasses
First Jack drops them and ends up breaking a lens, then toward the end of the book Jack's group comes and takes them.
Simon retrieved Piggy's glasses for him, after they had fallen onto the rocks as a result of Jack punching Piggy.
Simon
jack has taken everything from everyone already so why would he have to take glasses that wont help him in anyway.
In the novel "Lord of the Flies" by William Golding, Piggy's glasses are broken when Jack slaps him, causing the glasses to fall off and shatter. The breaking of Piggy's glasses is symbolic of the deterioration of order and civilization on the island.
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.
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.
Jack's group attacks the four boys in their hut because they see them as a threat to their power and control over the island. Roger, in particular, is driven by his sadistic nature and desire for domination, leading to the brutal attack on the boys in the hut.
Jack and his hunters break in and steal piggy's glasses
Ralph takes a makeshift spear to use as a weapon against Jack in "Lord of the Flies." He repurposes a stick, sharpens one end, and uses it to defend himself and confront Jack's tribe.