Not entirely sure if this is what you are looking for, but I just finished Steve Coll's "Ghost Wars", where he talks a little about how the Vietnam War affected the CIA.

By the late 1970's and 1980's, much of the CIA were Vietnam War veterans, veterans still haunted by the memories of their brothers in arms perishing at the hands of the Vietcong, which who were receiving arms and supplies from the USSR.

When the Red Army invaded Afghanistan, many intelligence officers saw not only opportunity to disrupt the interests of the USSR, but also sought revenge for their fallen brethren.

So without foresight or restraint, they began to arm Militants in Afghanistan providing even more resources to the particularly vicious commanders like Gulbuddin Hekmatyer, as they were the most effective in killing Soviet Troops.

Much of the arming of the Mujahideen in Afghanistan during its conflict of the USSR was because the CIA wanted Soviet blood to be spilled the same way American blood was spilled in Vietnam.