The Battle Hostile_encounter of Route Coloniale 4 ( called Name_conferral Chiến dịch Biên giới [ `` Border Campaign Military_operation '' ] in Vietnam ) was a battle Hostile_encounter of the First Indochina War Military_operation .

It took place Process_start along Route Coloniale 4 ( RC4 , also known as Highway 4 ) , a road used Using to supply Supply the French military base at Cao Bằng .