Editing Ho Chi Minh trail (section)

=== Truck relay system ===
Trucked supplies traveled in convoys from North Vietnam in relays, with trucks shuttling from one way station to the next. The vehicles were then unloaded and reloaded onto "fresh" trucks at each station. If a truck was disabled or destroyed, it was replaced from the assets of the next northern station and so on until it was replaced by a new one in North Vietnam. Eventually, the last commo-liaison station in Laos or Cambodia was reached and the vehicles were unloaded. The supplies were then cached, loaded onto watercraft, or man-portered into South Vietnam.<ref name=Nalty/>{{RP|218}}

Due to the increased effectiveness of "Commando Hunt", North Vietnamese transportation units usually took to the roads only at dusk with traffic peaking in the early morning hours. As U.S. aircraft came on station, traffic would subside until just before dawn, when fixed-wing gunships and night bombers returned to their bases. The trucks then began rolling again, reaching another peak in traffic around 06:00 as drivers hurried to get into truck parks before sunrise and the arrival of the morning waves of U.S. fighter bombers.<ref name=Nalty/>{{RP|218}} By the last phase of "Commando Hunt" (October 1970 – April 1972), the average daily number of U.S. aircraft flying interdiction missions included 182 attack fighters, 13 fixed-wing gunships, and 21 B-52s.<ref name=Glister>{{cite book|last=Glister|first=Herman|title=The Air War in Southeast Asia: Case Studies of Selected Campaigns|publisher=Air University Press|year=1993|url=https://apps.dtic.mil/sti/pdfs/ADA421686.pdf|archive-url=https://web.archive.org/web/20220125082216/https://apps.dtic.mil/sti/pdfs/ADA421686.pdf|url-status=live|archive-date=25 January 2022}}{{PD-notice}}</ref>{{RP|21}}

[[File:North Vietnamese Antiaircraft Weapons.jpg|thumb|upright=1.35|The evolution of PAVN [[anti-aircraft weapon]]s, 1965–1972.]]

The North Vietnamese also responded to the American aerial threat by the increased use of heavy concentrations of anti-aircraft artillery. By 1968 this was mainly composed of 37&nbsp;mm and 57&nbsp;mm radar-controlled weapons. The next year, 85&nbsp;mm and 100&nbsp;mm guns appeared, and by the end of ''Commando Hunt'', over 1,500 guns defended the system.<ref name=Prados/>{{RP|313}}

Of all the weapons systems used against the trail, according to the official North Vietnamese history of the conflict, the [[AC-130 Spectre]] fixed-wing gunship was the most formidable adversary. The Spectres "established control over and successfully suppressed, to a certain extent at least, our nighttime supply operations".<ref name=Pribbenow/>{{RP|261}} The history claimed that allied aircraft destroyed some 4,000 trucks during the 1970–71 dry season, of which the C-130s alone destroyed 2,432 trucks.<ref name=Pribbenow/>{{RP|261}}

A Spectre countermeasure was unveiled on 29 March 1972, when a Spectre was shot down on a night mission by a surface-to-air [[SA-7]] missile near Tchepone.<ref name=Prados/>{{RP|369}} This was the first U.S. aircraft shot down by a SAM that far south during the conflict. PAVN responded to U.S. nighttime bombing by building the 1,000 kilometer-long Road K ("Green Road") from north of Lum Bum to lower Laos. During "Commando Hunt IV" (30 April–9 October 1971), U.S., South Vietnamese and Laotian forces began to feel the North Vietnamese reaction to General [[Lon Nol]]'s coup in Cambodia and the subsequent closure of the port of [[Sihanoukville (city)|Sihanoukville]] to its supply shipments.<ref>{{cite book|last=Shawcross|first=William|title=Sideshow: Kissinger, Nixon, and the Destruction of Cambodia |date=1979 |publisher=Simon & Schuster |isbn=9780671230708|pages=112–127|url=https://books.google.com/books?id=RasqAAAAYAAJ}}</ref> As early as 1969 PAVN had begun its largest logistical effort of the entire conflict.<ref name=Glister/>{{RP|20}}

The Laotian towns of [[Attapeu]] and [[Salavan (city)|Salavan]], at the foot of the [[Bolaven Plateau]] were seized by the PAVN during 1970, opening the length of the Kong River system into Cambodia. Hanoi also created the 470th Transportation Group to manage the flow of men and supplies to the new battlefields in Cambodia.<ref name=Prados/>{{RP|191}} This new "Liberation Route" turned west from the trail at Muong May, at the south end of Laos, and paralleled the Kong River into Cambodia. Eventually this new route extended past Siem Prang and reached the [[Mekong River]] near [[Stung Treng]].<ref name=Pribbenow/>{{RP|382}}

During 1971 PAVN took Paksong and advanced to [[Pakse]], at the heart of the Bolaven Plateau region of Laos. The following year, Khong Sedone fell to the North Vietnamese. The PAVN continued a campaign to clear the eastern flank of the trail that it had begun in 1968. By 1968, U.S. Special Forces camps at [[Khe Sanh Combat Base|Khe Sanh]] and Khâm Đức, both of which were used by MACV-SOG as forward operations bases for its reconnaissance effort, had either been abandoned or overrun. In 1970, the same fate befell another camp at [[Dak Seang Camp|Dak Seang]]. What had once been a {{convert|20|mi|km|-1|order=flip|adj=mid|-wide}} supply corridor now stretched for {{cvt|90|mi|km|-1|order=flip}} from east to west.{{citation needed|date=October 2021}}