First, Hanoi decided not to build the main in¬filtration corridor in Cambodia, but to run it through South Vietnam's western mountains instead. However, the evidence shows North Vietnam determined to construct an alternate corridor in Cambodia's northeast. Communist cadres began filtering into Stung Treng Province later in late 1960. Some were Pathet Lao — northern Stung Treng is full of Laotians. Others were probably local tribesmen and Khmers from Hanoi's training camps.