Operation Dewey Canyon was the last major offensive by the 3rd Marine Division during the Vietnam War. It took place from 22 January through 18 March 1969 and involved a sweep of the People's Army of Vietnam (PAVN)–dominated A Shau and Song Đa Krông Valleys by the 9th Marine Regiment. Based on intelligence and captured documents, the PAVN unit in contact was believed to be the 9th Regiment.
The 56 days of combat were a tactical success but did not stop the overall flow of North Vietnamese men and matériel into South Vietnam. The 9th Marine Regiment and attached units were awarded the Army Presidential Unit Citation for their actions in Operation Dewey Canyon. Wikipedia
Lam Son 719 : the cargo must get through by On our terms : U.S. Marines in Operation Dewey Canyon, 22 January to 18 March 1969 by
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