Complex sentence: LZ Carolyn was situated in a location especially irritating to the NVA, astride one of the main access routes for the Viet Cong (VC) & North Vietnamese Army (NVA) to reach Saigon, its presence was a constant problem for them.
Split into simpler sentences: LZ Carolyn was situated in a location especially irritating to the NVA. Astride one of the main access routes to Saigon for the NVA and VC, its presence was a constant problem for them.