Below is a transcript of the letter;
That bright-eyed begger has been turnin' us against each other. Just yesterday we marched into battle, just like we've done a dozen times before. Ready and itching for a bit of the old blood and bone to start flying.
Then suddenly out of nowhere, he's bang in the middle of us. A flash of light and Orcs who've been fightin' alongside each other for years are at each other's throats.
It's one thing for us Uruk to murder each other, it's something else to have some Elf using us as his toys.