Complex sentence: A patrol of men from Company D of 3rd Recon were scouting 13-kilometers southwest of Da Nang, accompanied by a few platoons of soldiers from the Army of the Republic of Vietnam (ARVN).
Split into simpler sentences: A patrol of men from Company D of 3rd Recon was scouting 13 kilometers southwest of Da Nang. The Marine patrol was accompanied by a few platoons from the Army of the Republic of Vietnam (ARVN).