Many observers were more circumspect. As early as October 1969 (and possibly anticipating the loss of their Cambodian routes) PAVN had begun what was "probably their largest and most intense logistical effort of the whole war" by constructing and expanding their routes into northwestern Cambodia. The CIA estimated that the replacement of the supplies lost during the incursion would only take 75 days to achieve. As far as the long-term repercussions, there were three, all detrimental to the American cause: the loss of American political support by the Nixon administration, which would eventually lead to the fall of South Vietnam in 1975; the beginning of outright support of the Khmer Rouge by the North Vietnamese (who despised and distrusted their Chinese-supported comrades); and the spreading of general war throughout Southeast Asia.