Guard's Orders is a tome found in Act II of Diablo III.
It can be found in the Imperial Guard Supplies in the Khasim Outpost in the Stinging Winds, the container will appear first during The Road to Alcarnus quest.
It reads as follows:
Captain of the Guard, you are hereby ordered to send a band of your most loyal men to secure the Khasim Outpost. Control of the city hangs by a thread. The commoners are becoming restless, and it is imperative that we subdue them. Remain vigilant, for these may already be an outsider within our borders, looking to stir up trouble. — (Illegible Signature)