The Alshanai Rift was a region of space that bordered the Klingon Empire and the Federation.
Circa reference stardate 1/76 (circa 2230s), four planets within this area wished peace with both powers. However, they were subjected to attacks by Orion pirates, whose services were bought by the Klingons. The Klingons wished the worlds to abandon their ties to the Federation and join the Empire, on the basis that the Federation could not protect them from the pirates. (TOS - Worlds Apart novel: The Final Reflection)