The case of Mr. Tannenbaum had provoked what many war-crimes experts and Jewish leaders called deep complexities and passions, raising such questions as why a Jew would have collaborated with the Nazis, whether the persecuted can also be the persecutor and how such questions can be answered more than 40 years after the fact.
Some Jewish leaders, while disavowing sympathy for any collaboration with the Nazis, drew distinctions between those who volunteered to help the Nazis and those who thought they were saving their own lives by cooperating, often with the intention of easing the brutal life of fellow prisoners.
Kapos - from the German word Lagerkapo, or camp captain - were appointed by the SS, which supervised the camps, and enjoyed special privileges such as better food, clothing and housing. In return, they supervised the work of other inmates.
Source: NY Times