In fact, Parry, as a personal favour to YHWH (the incarnation of the God of the Jews, called JHVH in this book), manages to prevent the Holocaust from happening.
Tetragrammaton, the four Hebrew letters YHWH as the name of God, and various pronunciations given to them
the Tetragrammaton, the Hebrew name for God, sometimes written as YHWH (four letters)
Jah, shortened form of the divine name YHWH (also spelled Jehovah or Yahweh)
Tal Ilan's Lexicon of Jewish Names in Late Antiquity (2002), notes Yehoshua (יהושע), and the later Aramaic form Yeshua among many names containing Yah derived from YHWH.