During World War II, why didn't Jews pretend that they weren't Jews to avoid such harm?

This problem seems to stem from the idea that Jews are defined by religion rather than race. This was true before Hitler. In medieval Europe or tsarist Russia, Jews who converted to Christianity were no longer considered Jews. Of course, such people may be more strictly monitored than ordinary Christians.

But if this change is considered to be true, then this change has become a mature member of Christian society. Sometimes the new convert is so fanatical that he even becomes a very notorious anti-Semitic. However, under the leadership of Adolf Hitler, it did not do so. Race is the most important thing for the Fuehrer, but faith is not. The Nuremberg law promulgated in 1935 contains strict interpretations that can be regarded as Jews.

A person with three or four Jewish grandparents is considered a Jew. A person with one or two Jewish grandparents is considered naughty. Whether a naughty person is Jewish or not depends on his behavior. Marrying a Jew, making friends with Jews or expressing dissatisfaction with the government all make this person a Jew. On the contrary, marrying a non-Jew and being very loyal to the government will reduce the risk.

In Germany, it is very difficult, if not impossible, to hide your Jewish identity. The bureaucracy is very strong, and the statistics are almost perfect. A government official knows who your grandparents are. If three of them are Jews, your only hope is to flee the country as soon as possible. In other countries, the situation may be different, where the bureaucracy is often inefficient and the Nazis face many different obstacles, such as sabotage from local civil affairs or church authorities.

They often ask Jews to stand up (many people have done so! ) and then rely on local informants, circumcision and other physical characteristics. It should be taken into account that the situation in different occupied countries may be different. In France, when the Nazis arrested Jews, they often brought them the benefit of suspicion, because they didn't want to arrest a non-Jewish Frenchman. In Poland or Russia, they are not so cautious.