First appearance = the Wonder Woman feature in World's Finest Comics #246 (August-September 1977)
NOTE: This was the period when World's Finest Comics was a larger $1.00-sized comic book with multiple features and coincided with the period when the first season of the Wonder Woman TV show (starring Lynda Carter) was carried on the ABC network here in the U.S. and was set back in the 1940s.
Baron Blitzkrieg would later go on to become a villain for many other DC heroes, as he was in Roy Thomas' All-Star Squadron series.
The above scene from All-Star Squadron #7 (February 1982).
From Who's Who: The Definitive Directory of the DC Universe Vol. II (April 1985):