The Blitzkrieg was a mod that was announced by Zach Higgins on July 12, 2002. A screenshot was posted on that date in addition to another one on July 29.
Shortly after releasing Projekt: Vertilgung, a screenshot was posted of a supposed new project from Higgins, If, which looked virtually identical to The Blitzkrieg. Furthermore, the name of the screenshot was blitz1.gif, so it may simply have been a change of name.
Obviously a new number of graphics were made for the project, sadly none of which surfaced in other projects.