Editing Ho Chi Minh trail (section)

=== Ground operations against the trail ===
{{See also|Operation Left Jab|Operation Honorable Dragon|Operation Diamond Arrow|Project Copper|Operation Phiboonpol|Operation Sayasila|Operation Bedrock|Operation Thao La|Operation Black Lion}}
[[File:SOG hidden.jpg|thumb|[[PAVN]] troops on the trail (photo taken by a U.S. [[MACV-SOG]] team)]]

On the ground, the CIA and the RLA had initially been given the responsibility of stopping, slowing, or, at the very least, observing the enemy's infiltration effort. In Laos, the agency began [[Operation Pincushion]] in 1962 to accomplish that goal.<ref name=Conboy/>{{RP|85–91}} The operation evolved into [[Operation Hardnose]], in which CIA-backed Laotian irregular reconnaissance team operations took place.<ref name=Conboy/>{{RP|115–122}}

In October 1965, [[General William Westmoreland|General Westmoreland]] received authorization to launch a U.S. cross-border recon effort. On 18 October 1965, the first mission was launched "across the fence" into Laos by the [[Military Assistance Command, Vietnam Studies and Observations Group]] (MACV-SOG).<ref>{{cite book|last1=Maitland|first1=Terrence|last2=McInerney|first2=Peter|title=The Vietnam Experience: A Contagion of War|url=https://archive.org/details/vietnamexperienc00mait|url-access=registration|publisher=Boston Publishing Company|year=1983|isbn=0939526050|pages=123–4}}</ref> This was the beginning of an ever-expanding reconnaissance effort by MACV-SOG that would continue until the operation was disbanded in 1972. Another weapon in the U.S. arsenal was unleashed upon the trail on 10 December 1965, when the first [[B-52 Stratofortress]] bomber strike was conducted in Laos.<ref name=Prados/>{{RP|158}}

A common historical perspective supports the efficacy of the campaigns (despite their failure to halt or slow infiltration), as they did restrict enemy materiel and manpower in Laos and Cambodia. This viewpoint pervaded some official U.S. government histories of the conflict. John Schlight said of the PAVN's logistical apparatus, "This sustained effort, requiring the full-time activities of tens of thousands of soldiers, who might otherwise have been fighting in South Vietnam, seems proof positive that the bombing of the Ho Chi Minh Trail had disrupted the North Vietnamese war effort."<ref>{{cite book|last=Schlight|first=John|title=A War Too Long: The USAF in Southeast Asia, 1961–1975|publisher=Air Force History and Museums Program|year=1996|url=https://media.defense.gov/2010/May/25/2001330271/-1/-1/0/AFD-100525-077.pdf|archive-url=https://web.archive.org/web/20181017082219/https://media.defense.gov/2010/May/25/2001330271/-1/-1/0/AFD-100525-077.pdf|url-status=dead|archive-date=17 October 2018|page=56}}{{PD-notice}}</ref>

Despite U.S. anti-infiltration efforts, the estimated number of PAVN infiltrators for 1966 was between 58,000 and 90,000 troops, including five full enemy regiments.<ref name=Prados/>{{RP|182}} A June 1966 DIA estimate credited the North Vietnamese with {{convert|600|mi|km|sigfig=1|order=flip|abbr=on}} of passable roads within the corridor, at least {{convert|200|mi|km|sigfig=1|order=flip|abbr=on}} of which were good enough for year-round use.<ref name=Doyle>{{cite book|last1=Doyle|first1=Edward|last2=Lipsman|first2=Samuel|last3=Maitland|first3=Terrence|title=The Vietnam Experience The North|publisher=Boston Publishing Company|year=1986|isbn=|page=46}}</ref> In 1967 Senior Colonel (later General) [[Dong Sy Nguyen|Đồng Sỹ Nguyên]] assumed command of the 559th Group. In comparison to the above DIA estimate, by the end of the year the North Vietnamese had completed 2,959&nbsp;km of vehicle capable roads, including 275 kilometers of main roads, 576 kilometers of bypasses, and 450 entry roads and storage areas.<ref>Joint Chiefs of Staff, ''MACSOG Documentation Study'', Appendix D, pp. 293–294.</ref>

It was learned by U.S. intelligence that the enemy was using the Kong and Bang Fai Rivers to transport food, fuel, and munitions shipments by loading materiel into half-filled steel drums and then launching them into the rivers. They were later collected downstream by nets and booms. Unknown to the U.S., the North Vietnamese had also begun to transport and store more than 81,000 tonnes of supplies "to be utilized in a [[Tet Offensive|future offensive]]".<ref name=Pribbenow/>{{RP|208}} That future offensive was launched during the lunar new year [[Tết]] holiday of 1968, and to prepare for it, 200,000 PAVN troops, including seven infantry regiments and 20 independent battalions, made the trip south.<ref name=Doyle/>

Throughout the war, ground operations by conventional units were somewhat limited to brief incursions into border sanctuaries. One notable operation was [[Operation Dewey Canyon|Dewey Canyon]] which took place from 22 January to 18 March 1969 in I Corps. During the operation, the [[9th Marine Regiment]] attempted to interdict PAVN activity in the Da Krong River and A Shau Valleys. Ground units briefly entered the border areas of Laos during fighting with elements of the PAVN 9th Regiment.<ref>{{cite book|last=Pike|first=Thomas|title=Operations and Intelligence, I Corps Reporting: February 1969|publisher=US Army|url=http://www.tfpike.com/i-corps-feb--69.html|archive-url=https://web.archive.org/web/20161011134008/http://www.tfpike.com/i-corps-feb--69.html|url-status=dead|archive-date=11 October 2016|year=1969|isbn=9781519486301|page=193}}</ref><ref>{{cite book|last=Smith|first=Charles|title=U.S. Marines In Vietnam: High Mobility And Standdown, 1969 |publisher=History and Museums Division, Headquarters US Marine Corps|url=https://www.usmcu.edu/Portals/218/U_S_%20Marines%20in%20Vietnam%20High%20Mobility%20and%20Standown%201969%20%20PCN%2019000310300.pdf|year=1988|isbn=9781494287627|pages=30–50}}{{PD-notice}}</ref>