Signs of impending communist action were noticed among the allied intelligence collection apparatus in Saigon. During the late summer and fall of 1967 both South Vietnamese and U.S. intelligence agencies collected clues that indicated a significant shift in communist strategic planning. By mid-December, mounting evidence convinced many in Washington and Saigon that something big was underway. During the last three months of the year intelligence agencies had observed signs of a major North Vietnamese military buildup. In addition to captured documents (a copy of "Resolution 13", for example, was captured by early October), observations of enemy logistical operations were also quite clear: in October, the number of trucks observed heading south through Laos on the Hồ Chí Minh Trail jumped from the previous monthly average of 480 to 1,116. By November this total reached 3,823 and, in December, 6,315. On 20 December, Westmoreland cabled Washington that he expected the PAVN/VC "to undertake an intensified countrywide effort, perhaps a maximum effort, over a relatively short period of time."