The supply capacity of the trail reached 20 to 30 tonnes per day in 1964 .
Supply capacity was estimated by the U.S. that 12,000 ( actually 9,000 ) North Vietnamese regulars had reached South Vietnam that year .
The supply capacity of the trail reached 20 to 30 tonnes per day in 1964 and it was estimated by the U.S. that 12,000 ( actually 9,000 ) North Vietnamese regulars had reached South Vietnam that year .