In mid-March U.S. intelligence learnt that the People's Army of Vietnam (PAVN) 27th Regiment was moving south of the DMZ in an attempt to cut Route 9.

A counter-infiltration operation was planned whereby the 3rd Squadron, 5th Armored Cavalry and the 1st Battalion, 11th Infantry Regiment would patrol the Khe Chua Valley north of Firebase Fuller.

[1]: 58–9 [2]: 57 The operation commenced on 23 March with the 3/5 Cavalry moving into the Khe Chua Valley meeting limited opposition.

[1]: 60 Operation Montana Mauler concluded on 3 April, with the US claiming the PAVN 27th Regiment had lost approximately 300 killed.

[1]: 60 This article incorporates public domain material from websites or documents of the United States Marine Corps.