The exact timing of the Communists' decision on Cambodia is far from clear. A notebook kept by a high- level Lao Dong Party member in Laos suggests, however, that the "Cambodian front" opened prior to April 1968. The testimony of the defector most knowledgeable about the flow of Cambodians south supports the notebook. The rallier indicated that starting in January 1968 the annual rate of Khmer infiltration to the COSVN area increased sharply, and that thereafter the large majority of infiltrators were soldiers rather than civilians.* Finally, there is the evidence,of the rebellions themselves. Serious fighting broke out in the southwest in February 1968; in the northeast in March.