A game of Fortitude lasts 16 hands during which you will play a trick-taking game against a German bot. Each round consists of eight tricks--four played in the Calais, France location and four in Trondheim, Normay--with a final ninth trick, that you're trying to lose, played in Normandy.
Between rounds, if you've played tactically then you can earn upgrades that help modify your future cards. But be forewarned because you'll draw periodic setback cards that might well turn a winning position into a loss.
While you want to win tricks in Calais and Trondheim, winning in Normandy will eventually clue Germany into its importance to the Allied forces. So every Normandy win requires you to fill in spaces in a limited polygonal area. If you can, then you continue your campaign. But if you can't fill in the required boxes, you lose.
Fortitude is a trick-taking and write game that asks if you can successfully deceive the Germany military intelligence long enough to ensure D-Day happens as planned.
Andrew finds Fortitude to be an uneven experience in this Meeple Mountain review.