Perhaps it's because, unlike others like Lanzmann, Resnais, Spielberg, et al., Ken Burns and his crew of expert documentarians come to the subject with all their finely-tuned skills in presenting important historical events, this is, for me, the most powerful, and upsetting rendering of the subject I have ever seen. Although the subject is, ostensibly, the role the United States played--or did not play--in dealing with the murder of millions of innocent civilians merely because they were Jewish, what I found most impressive was the focus on the transformation of ordinary, often happy lives throughout Europe into a brutal, horrifying nightmare. As one of the interviewees puts it, the emphasis on the death-camps, while certainly justified, tends to overlook the everyday brutality of innocent men, women and, equally, children being routinely and heartlessly ostracized by their "friends," humiliated, beaten, thrown from the rooftops of building, burnt, and, if lucky, merely shot.
It's very hard to talk about this film, but one must acknowledge the great achievement of these filmmakers.
