The Breaking of the Fellowship is the tenth chapter of Book Two of The Fellowship of the Ring.
The Fellowship arrives at Amon Hen, near the falls of Rauros with the intention to determine which route to take. Aragorn gives Frodo an hour to decide which route he deems best, but while alone, he is encountered by Boromir, who, seduced by the One Ring, attempts to take it from the hobbit by force. Frodo escapes, but meanwhile, a band of Uruk-hai sent by Saruman has attacked the rest of the Fellowship. Many of them are killed, but Boromir, having shaken off the ring's influence, is slain himself defending Merry and Pippin. Aragorn arrives too late to save him, and finds that the hobbits have been carried off by the uruks.
Meanwhile, Frodo has attempted to leave alone and unseen for Mordor, but Sam catches up to him and convinces Frodo to take him along. Aragorn, Legolas, and Gimli arrive too late to hinder Frodo and Sam, and decide to track down the uruks and save the remaining hobbits.