 Complete the following phrase:  Upon the division of Vietnam in 1954 into North and South, Quảng Trị became the northernmost province of the Republic of Vietnam. The Vietnamese Demilitarized Zone lay in the province. Beginning 1964, the province gradually became a center for American bases, particularly after October 1966, when the 3rd Marine Division moved to bases just south of the demilitarized zone. In 1966, North Vietnamese forces also began occupying the northern region and pushing deeper into the province. The provincial capital, Quảng Trị City, was overrun and occupied briefly by Communist troops in April 1967, and was a principal battleground during the 1968 Tet Offensive when it was again overrun by North Vietnamese troops and held for a short period before being recaptured by South Vietnamese government and U.S. forces. The Battle of Khe Sanh 1968 was a part of the Norths steady efforts to occupy the whole of the province. After Khe Sanh was evacuated in July 1968, the North Vietnamese continued their efforts to take the entire province. The most notable achievement of the North Vietnamese offensive in 1972 was capturing Quảng Trị First Battle of Quảng Trị, although they lost much of the territory gained during the South Vietnamese counter-offensive from June through September 1972 