The
Battle of Route Coloniale 4 (called
Chiến dịch Biên giới [
Operation Border Zone] in Vietnam) was a battle of the
First Indochina War. It took place along Route Coloniale 4 (RC4, also known as Highway 4), a road which was used to supply the French military base at
Cao Bang. French military traffic along the road had previously been subject to
an ongoing series of ambushes during 1947-1949.