(1) Posted by Hauke Reddmann [Saturday, Jan 8, 2022 17:40]
2# theme
I probably could browse through all of Udo's 2# theme book,
but crowdsourcing might be more effective:
White moves a piece out of a black battery line, asking for a check.
But the moving white piece created a half pin of the black checking piece,
and giving the check thus pins the other piece which thus can't
defend against the now following crosscheck.