sign one's own death warrant (или death-warrant)

Hitler in declaring war against the Sovit Union, has signed his own death warrant. He and his Nazi barbarians are now marching to their doom. (W. Foster, ‘The Twilight of World Capitalism’, ch. X) — Объявив войну Советскому Союзу, Гитлер подписал свой смертный приговор. Он и его нацистские варвары идут теперь к своей гибели.