With the focus in northern I Corps being in the west during the first months of 1968, the NVA countered in May with a major offensive in the eastern DMZ. The 320th NVA Division struck first with an attempt to close the Cua Viet River, the main supply route for Dong Ha Combat Base. That attempt was stopped by the Fourth Marines at the famous battle for Daido.
On May 8th 3/3 discovered and overran an NVA regimental base camp in Leatherneck Square and subsequently uncovered a huge cache of arms, ammunition and supplies destined to support the eastern DMZ offensive. Enemy contact in the area spiked dramatically during May and early on a badly bloodied 320th withdrew to sanctuary north of the DMZ. In the midst of this activity General Ray Davis assumed command of the 3rd Marine Division. He immediately changed tactics from manning the static Alpha positions to one of high mobility. Battalion positions, like Alpha 3, became company positions and suddenly line companies were roaming the countryside and moving by helicopter with much more frequency.
On May 25 3/3 began choppering into the Cua Viet area to assist the Fourth Marines who were in heavy contact with a refitted 320th Division. What followed was a week of intense, night and day combat. Units from the Third, Fourth and Ninth Regiments plus US Army and ARVN troops corralled the NVA division into a cordon where they were destroyed by supporting arms. In the field it was know as the Second Battle of Dai do or the Mini Tet. Military scholars have since renamed it the Battle for Dong Ha and the two incursions cost the 320th 3000 dead. It was not without high cost to friendly forces, however. 3/3ís command chronology for May lists 50 KIA and 350 WIA.