In December, intelligence became conclusive that PAVN units supporting Khmer Rouge operations in Cambodia began returning to the border areas. In Laos and Cambodia, there was also an unusual expansion of infiltration. In North Vietnam, there was a noticeable increase in military recruitment. In January, Defense Intelligence Agency officers briefed Secretary of Defense Melvin Laird to state that PAVN would attack after the Tết holidays and that the offensive would involve the widespread use of armored forces. Laird was unconvinced and told the U.S. Congress in late January that a large communist offensive "was not a serious possibility"