There were some exceptions to the fighting in South Vietnam being very different from that of the past, for the shifting intensities and scale of combat sometimes included variations of conventional war. The invasion of Cambodia in April-June 1970, the South Vietnamese operation in Laos in February-April 1971 and the North Vietnamese offensives in March-April 1972 and March-April 1975 are clear examples of conventional operations. But the majority of the fighting remained non-conventional. The dilemma for American commanders was the continued threat of large-scale operations in an environment where relatively small-scale operations were the rule. Neither extreme, of the possible scale of operations could be ignored.

*** When US forces entered combat in 1965, the VC and NVA forces had recently changed their tactics from small-unit to larger unit operations. They were enjoying a considerable degree of success, and, as General William C. Westmoreland said, "The South Vietnamese government-already exhausted by a decade of struggle-was thus faced with defeat."128 Consequently, the initial phase of fighting by the Americans stressed "arresting the losing trend, stifling the enemy initiative, protecting the deployment of our forces, and providing security to populated areas to the extent possible."129

The "fire brigade" approach extended throughout 1965, and, according to General Westmoreland, "Attacks by air and artillery fire constituted the bulk of our offensive operations in early 1966 until our ground strength reached appropriate and effective levels." During the early phase of the war, ground operations were thus launched only against enemy forces constituting "an immediate and grave threat."130 By the spring of 1966, the possibility of an immediate enemy victory had disappeared, and, according to Lieutenant General Richard G. Stilwell, "the initiative began to pass to the allies."131

From the Battle of the Ia Drang Valley in October-November 1965 through Junction City in February-May 1967, US Army commanders sometimes employed division or multidivision-sized forces to destroy larger VC and NVA units.132 Division or larger size units were also used after 1967 such as in the area around Khe Sanh in early 1968 or following the Tet offensive in January 1968.

Large units frequently conducted spoiling attacks or reconnaissances in force into enemy base areas. The focus on semi-conventional, large-unit operations came at the expense of the local pacification effort.133 From the Army's view, however, such a focus was essential given the circumstances of the US entry into the war. General Westmoreland explained, "We had learned that we had to take the fight to the enemy if pacification was ever to succeed." The threat of enemy main force units attacking local security forces had to be eliminated.134