Secret Unit Deployment | Board Game Mechanic

In Secret Unit Deployment games, some (or all) pieces enter the board in secret, and only the player controlling certain playing pieces has perfect information about the nature (or even the whereabouts) of those pieces. Other players will not know where those pieces are located on the board, or they may know where pieces are, but not know the details (such as strength or type) of these pieces. This mechanic is often used in wargames to simulate "fog of war".