13 Days is Twilight Struggle, streamlined into 45 minutes. It loses much of Twilight Struggle's nuance, but it plays much faster.
13 Days has the two players playing Kennedy and Khrushchev during the Cuban missile crisis. Your points are Prestige, and assuming you make it through 3 rounds, the crisis ends and the side with more Prestige wins.
The primary way to earn Prestige is through Agenda cards. Each round, each player receives three Agenda cards, each identifying a way to earn Prestige. Each player marks on the board the three cards they drew, but secretly selects one to actually pursue. At the end of the round, the cards are revealed and the points awarded. It's possible for a player's Agenda to actually award points to their opponent if they're not careful.
Agendas are typically scored based on Domination or the DEFCON track. The board has various military, political and world opinion spaces; Domination is as simple as whoever has more wooden cubes there. The DEFCON track is divided into military, political, and world opinion, and has many spaces to track how close each power is to launching a nuclear weapon.
Each player then receives 5 Strategy cards. The players will alternate playing 4 of them. Neutral cards, or cards associated with the player can be played for the text effect, or to Command, allowing them to add or remove cubes of their own color. An opponents cards are always played for Command, but their opponent gets to use the text effect first. Part of the strategy is playing an opponent's cards when they benefit them the least.
Command is a bit innovation over Twilight Struggle. While simpler, you just add or remove cubes, for every cube beyond the first that you add or remove from an area, you adjust the matching DEFCON by 1, escalating if you added cubes, deflating if you removed cubes.
Managing DEFCON is the inspired bit. At the end of each round, the DEFCON tracks are checked. If someone reached DEFCON 1, they launch and lose. If someone has all three of their tracks at DEFCON 2, they launch and lose. (It's possible for both sides to lose.) This creates the sort of back and forth of the real missile-crisis; each side has incentive to push hard, but also to occasionally pull back. Pick a fight you've decided you don't care about and sacrifice it to pull back from the brink. Of course, with your breathing room, maybe push harder somewhere else.
Like Twilight Struggle, much of the game will come from learning the cards. On the up side, there are far fewer cards, and the range of possibilities is smaller. On the down side, both of my first two games ended with someone launching nuclear missiles, largely by accident because of unfamiliarity with the cards.
Overall, I've enjoyed it, and hope to play some more.