to talk a lot in a loud voice, usually boasting or trying to threaten someone; when someone boasts or talks loudly with little effect;  wrzeszczeć; odgrażać się, przechwalać się; przechwałki; pogróżki

They had no idea it was all bluster and obeyed him.

Nie mieli pojęcia, że to czcze pogróżki i posłuchali go.