"Enemy Action: Ardennes is the first in a series of card-driven war games on pivotal operations and campaigns in World War II, from John Butterfield, designer of RAF, D-Day at Omaha Beach, Ambush! and Hell’s Highway. Each game in the series allows for play by two players or one player, playing either side in the conflict.
"Enemy Action delivers fun, tense wargaming with a focus on command and capabilities:
- Low complexity with constant decision points for both sides;
- Two-player competition;
- Solitaire play of either side with an innovative system governing enemy command and tactics;
- Card-driven impulse system, with multi-purpose cards that can be played to activate formations, implement command events, or gain tactical advantages in combat.
- Diceless and chartless combat system – players draw combat chits that build a narrative of each combat.
"EA: Ardennes portrays the German offensive against the western Allies in December 1944 -- the Battle of the Bulge. Each player controls the German or Allied (US and British) side. If playing solo, the game system controls the other side.
- Map scale: 2.5 miles per hex. Hexes are oversized for easy counter handling.
- Unit Scale: Regiments, brigades and divisions
- Time scale: One day per turn, with several impulses in each turn."
BGG wiki page with many clarifications and hints and errata:
Enemy Action: Ardennes German Solo FAQ