The two Uruk-captains are going through the "dead" Frodo's belongings, when they stumble upon his Mithril-shirt. Que instant civil war between orcish warbands.
Wasn't Gorbag a smaller orc?!
Only in the movie. Both of them were Uruks in the novel, but that doesn't really matter in the end. As I've written many times, this project is about my own interpretation of Tolkien's work, as well as my own reimagining of the source material.