The Reubenites, Gadites and half-tribe of Manasseh cried to God and defeated which people?

Answer: The Hagrites

They cried out to God in battle and trusted Him, so the Hagrites and their allies were delivered into their hands.

“They waged war against the Hagrites, as well as Jetur, Naphish, and Nodab.”— 1 Chronicles 5:19 (BSB)