Answer based on context:

In May 1959 the first major steps to prepare infiltration routes into South Vietnam were taken; Group 559 was established, a logistical unit charged with establishing routes into the south via Laos and Cambodia, which later became famous as the Ho Chi Minh trail. At about the same time, Group 579 was created as its maritime counterpart to transport supplies into the South by sea. Most of the early infiltrators were members of the 338th Division, former southerners who had been settled at Xuan Mai from 1954 onwards. Regular formations were sent to Southern Vietnam from 1965 onwards; the 325th Divisions 101B Regiment and the 66th Regiment of the 304th Division met US forces on a large scale, a first for the PAVN, at the Battle of Ia Drang Valley in November 1965. The 308th Divisions 88A Regiment, the 312th Divisions 141A, 141B, 165A, 209A, the 316th Divisions 174A, the 325th Divisions 95A, 95B, the 320A Division also faced the US forces which included the 1st Cavalry Division (United States), the 101st Airborne Division, the 173rd Airborne Brigade Combat Team, the 4th Infantry Division (United States), the 1st Infantry Division (United States), and the 25th Infantry Division (United States). Many of those formations later became main forces of the 3rd Division (Yellow Star Division) in Binh Dinh (1965), the 5th Infantry Division (Vietnam) (1966) of 7th Military Zone (Capital Tactical Area of ARVN), the 7th Division (Vietnam) (created by 141st and 209th Regiments originated in the 312th Division in 1966) and 9th Division (Vietnam) (first Division of National Liberation Front of Vietnam in 1965 in Mekong Delta), the 10th Dakto Division in Dakto - Highland in 1972 south of Vietnam.

Which divisions met US forces at the Battle of Ia Drang Valley?
325th Division