That the NLF could take the massive political-ideological potential it had stirred up and use it to form a cohesive resistance movement was possible due to three factors: first, the strict yet decentralised nature of its organisation kept its operations effective and resistant to compromise; second, support from North Vietnam, China, and Russia ensured the availability of resources necessary for the movement; and third, highly appropriate and effective military tactics were employed to yield maximal results on its enemy. In this way, the NLF was able to cause sufficient sustained havoc and inflict enough damage on the American forces to coerce their withdrawal.
The key feature of the NLF's organisation was its decentralisation. Tightly organised three-man cells, the “basic unit in any communist organization, in Viet-Nam or elsewhere”, frequently operated independently, privy only to information necessary for their immediate objectives. Special activities cells, operating in rural and urban areas, often remained non-operational and completely segregated from any NLF activity until ordered to strike, when they carried out special tasks such as assassination and kidnapping. The NLF tried to ensure that its sapper cells, which carried out attacks on targets including government buildings, communication and transportation centres, port and storage facilities, vehicles, and key public figures, were similarly unlikely to reveal compromising information: sappers were picked from the most ideologically devoted members of the NLF, and information given to these cells was relevant only to immediate targets. This tight organisational structure and strict control of information ensured that when an NLF cell was captured, it could not reveal the location or activities of other units.
For larger objectives, cells were combined into groups, but even these were designed to limit damage resulting from capture. For example, paramilitary units (semi-professional groups of civilian operating in their home territory) were trained to operate in teams of up to nine cells when undertaking sabotage missions, carrying out small strikes, performing ordered executions, and spreading pro-NLF propaganda. If compromised, however, a member of such a cell could only betray other members of the small attack group, usually fewer than thirty people.
Travelling up the chain of command, the decentralisation of NLF control becomes even more evident. Even analysts who stressed the importance of an external element of communist control, such as Robert O'Neill, recognised that guerrilla operations “mounted in 1959 and afterwards could not have been directly controlled from Hanoi because the scope of these operations was too localised.” O'Neill called the control exercised by Hanoi over the Central Office for South Vietnam (COSVN) as limited as that between the Australian Government and General Blamey in the Middle East during the Second World War. The organisational structure of NLF units varied so much between regions that, according to Douglas Pike, another contemporary analyst, “what is a common pattern in the Mekong Delta may be unknown in the Hue area.” With such a high level of decentralisation and local autonomy, it was difficult for the U.S. Military and ARVN to make accurate or useful generalisations about the nature of insurgency, and even harder to follow the NLF chain of command to identify leaders or key personnel.
To add to American confusion, the NLF was not the only resistance movement in the South at the time. Completely separate organisations, imprecisely bundled with the NLF as "Vietcong" by the Americans, operated throughout the South. The People's Liberation Armed Force and the People's Revolutionary Party are but two examples. The organisation of resistance was so decentralised and locality-specific that even understanding the nature of their enemy was an all-but-impossible task for the U.S. and GVN.
Though the NLF retained strict control over its own operations, it was thoroughly dependent on indirect support from North Vietnam, which was in turn vitally sustained by military and economic aid from China and Russia. By the end of 1966, North Vietnamese imports by sea had risen to about one million metric tons, arriving in Haiphong from Soviet and Chinese ports. An additional 420,000 tons came in to Hanoi by rail from China in 1966. By 1967, imports had risen 45 percent, with one quarter coming from China and the remaining three quarters from the U.S.S.R. and Soviet Bloc nations. Without Soviet and Chinese support, North Vietnam would have been isolated, more open to attack, and of less use to the NLF in the South.
In turn, the North concentrated its resources on aiding the resistance in the South. An estimated ten thousand tons of war materiel per week was “trucked, biked, boated, and carried down the [Ho Chi Minh] Trail” to aid the NLF during peak periods. Many personnel in COSVN headquarters and a large proportion of the military supplies used by the troops under its control were lent by North Vietnam. Furthermore, the NLF could rely on actions of the NVA to provide diversions in times of crisis. In mid-1967, for example, North Vietnamese General Vo Nguyen Giap saved the bulk of the NLF in War Zone C from destruction with his series of offensives “aimed at distracting American attention from the southern provinces before Westmoreland had time to establish some degree of permanent control”, causing a significant concentration of U.S. resources to be diverted to the Dak To and Kontum areas further North. This North Vietnamese support that the NLF had come to rely on was virtually guaranteed to continue unabated when American officials, fearing Soviet or Chinese retaliation, publicly and repeatedly announced a policy of non-involvement in the North during the early Johnson era.
