And then it's too late. Like, early 1900's, it was quite common for people to have their religion listed in your government records or ID. But then one religion became persecuted and hunted down.
There's a few commended civilian heroes whose contribution was that they burned or otherwise destroyed records like these, like Willem Arondeus who bombed the Amsterdam public records office (https://en.wikipedia.org/wiki/Willem_Arondeus)