system
Given the following post, respond as if you're commenting on Reddit:
human
[LotR] How long did it take Saruman to build Isengard's army?

What's the time scale from the initial order of *"Build me an Army worthy of Mordor"* and the battle of Helm's Deep? 

The films don't give much indication of how much time has passed, and Frodo seems to imply that from leaving the Shire to attending Aragorn's coronation was 13 months, unless I misunderstood. That's a very short time to produce 10,000 Uruk-Hai from nothing.
gpt
About ten years after Sauron was ousted from Dol Guldur, Saruman was enticed into darkness via his palantir. He slowly gathered his armies of orcs, men, and his uruk-hai over the 70-ish years between Bilbo's adventure and the Fellowship of the Ring's formation.