The valley derives its name from the nearby Drang River in Vietnam's Central Highlands, was the site  of the first major encounters between U.S Army and the People's Army of Vietnam (PAVN).

Ly Thuong Kiet Campaign by Viet Minh in 1951 also known as Nghia Lo Battle was a military operation to remove the French posts at Nghia Lo in Yen Bai. All Viet Minh's attempts were without success, but the operation left good lessons to Viet Minh's commanders and soldiers. And they did show that they learned the lessons through their susequent campaigns...

Son My had been a little peaceful village bordered to the south by the Tra Khuc River and to the east by the East Vietnam Sea. Son My was divided into different hamlets, designated My Lai 1, 2, 3, 4 respectively.

Phu Tho Province is located in the North-West of Vietnam; bordered to the north-east by Tuyen Quang Province, to the east by Vinh Phuc Province, to the south-east by Ha Tay Province (Hanoi now), to the south by Hoa Binh Province, to the west by Son La Province and to the west and north-west by Yen Bai Province.

Quang Trung Campaign, or Ha Nam Ninh Campaign, was from 28-May to 20-June-1951. The battlefield was in the former Ha Nam Ninh Province which are three separate provinces now: Ha Nam, Ninh Binh, Nam Dinh. Major battles were on or near the Day River, hence the name Battle of the Day River as known to the French.

Tran Hung Dao Campaign 1950-1951 also known as Trung Du Campaign to the Viet Minh. During the campaign there were important battles at Vinh Yen, and it is known as the Battle of Vinh Yen to the French. The battle took place in 2 phase: 26 to 30-December-1950 and 12 to 17-Jan-1951.

April 1952, Raoul Salan was appointed to be the Commander in Chief of the French Forces in Indochina after the death of the predecessor De Lattre and the defeat of French forces in the Battle of Hoa Binh.

By mid 1954, the French had realized that it had lost the war to the Viet Minh and would not want to fight further. The Geneva Conference was held on the 20th and 21st of July 1954 to solve the problems in Indochina producing a number of agreements to settle the war. The set of agreements was called the Geneva Accord.

After the Geneva Accord in 1954, the north and the south of Vietnam was temporarily divided at the 17th parallel and the Ben Hai River was the temporary military demarcation line. The Demilitarized Zone (or DMZ) of no more than 5km in width was created on either side of the Ben Hai River.