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.
Changes were basic, as Higgins intended it was the mapping that should be the main focus of the mod. As Projekt: Vertilgung was still underway, the mod did not get finished.
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.