Interesting post by Gordis above. I'll have to reread parts of LOTR (not
at hand now). Trying to put the movie out of mind
, what were the motivations of the various orc parties? The Moria lads were out for revenge, but precisely why were the other two bands there? Presumably (?) Saruman's bird spies gave him intel that made him suspect some sort of hobbits/wizards were there. But why were Sauron's lot there? Perhaps detected by outlooks on the east bank of the Anduin? As to orc mental abilities/resistance to the Ring, how about Gorbag or his chum Grisnakh having enough sense to hide with it in some mountain fastness and let the two sides go at it, with Sauron partially distracted searching for the Ring and the G. orcs hoping they'll wear each other out. Picture a situation not unlike Poland between WWI and II, existing only as long as Germany and the U.S.S.R. are distracted/weak.