This hidden set-up war game is an unusual WWII adaptation of the classic L'Attaque. What makes it most unusual is that the rules are dated 11/44, which means it must have been one of the first French games published after the liberation.
This is a more complex game than L'Attaque or its successor Stratego. Its name translates as "The Lightning War" (or Blitzkrieg), and this is reflected in the mix of pieces.
Whereas L'Attaque and its successor Stratego simply used numerically ranked pieces, this game includes a host of WWII-era innovations as well, with pieces representing parachutists, bombers, anti-aircraft guns, delayed-action bombs, flying bombs and a tanker-truck that must survive to keep the bombers flying. Missing from the mix is any kind of armored unit, but there are "magnetic fences" that somehow disable the engines of aeroplanes.
Movement and combat is much more flexible than in the basic L'Attaque. Pieces may move in any direction, including diagonally, and may attack any piece orthogonally adjacent. To win, players must capture both the opponent's flag and its "secret plan".