Blitz == lightning
you know this term from football, when the defense comes roaring in in an effort to take the offense's ball as quickly as possible (you didn't think I knew anything about football, did you?!).
Krieg == war
just plain ol' everyday war, no specifics dealing with chemicals or viri and genetically altering bacteria or radioactive materials. just war
Hitler's stormtroopers (you don't think George Lucas made that word up, do you?) went in, and tried to take over certain land areas as quickly as possible, destroying anything that got in the way with little to no warning.
hence: Blitzkrieg... or, lightning (fast) war.
(In German, all nouns are capitalized)