Kriegspiel (German for "War Game") is a chess variant of imperfect information. The premise is that, like war, you can see your own position, but not that of your opponent. You follow the rules of normal chess, and some information is given to you, but otherwise you must deduce where your opponents pieces are in order to win. All information that is shared by the game is shared to both black and white. There are many variations of Kriegspeil, and each variation reveals different information. The more information you have, either directly or though deduction, the easier it is to win!
To play Kriegspiel you only need to know the rules of chess. All moves must conform to the normal rules of chess. When you make a move, it is announced and the turn changes - but the piece and square are not announced. If you attempt to make an illegal move, the attempt will be announced to both players. When it is your move, you can request 'Are there any pawn captures available?'. If there are, you must try at least one. When an 'impossible' move is attempted (for example moving a knight like a bishop or requesting pawn captures when there are no pawns), the action is simply ignored.
Like chess, the game is over when a player is checkmated or stalemated, a draw is agreed, or a player resigns. When the game is finished you will have the pleasure to replay the full game and see how both you and your opponent was moving (and hilarity usually ensues).
Listed below are all the possible announcements that can be shared with both players.