The Royal Game of Ur, also known as the ‘Game of Twenty Squares’, is a two-player strategy race board game first played in ancient Mesopotamia during the early third millennium BC. The game is probably a direct ancestor of the tables, or backgammon, family of games still popular today. The Game of Ur is played using two sets of seven checker-like game pieces. One set of pieces is white with five black dots and the other set is black with five white dots. As shown below, the gameboard comprises two rectangular sets of boxes, one containing three rows of four boxes each and the other containing three rows of two boxes each, connected by a further two boxes.
The object of the game is for a player to move all seven of their pieces along the course (two proposed versions of which are shown at below) and off the board before their opponent. On all surviving gameboards, the two sides of the board (in blue) are identical, representing the ‘safe’ spaces belonging to each player. When a player's piece is on one of their own squares, it is safe from capture. When a piece is on one of the eight squares in the middle of the board (in green), an opponent's pieces may capture it by landing on the same space. The captured piece is removed from the board so that it must restart the course from the beginning. There can never be more than one piece on a single square at any given time, so having too many pieces on the board at once can impede a player's mobility.
Gameplay: Movements are determined by rolling a set of four-sided, tetrahedron-shaped dice. Two of the four corners of each die are marked and the other two are not, giving each die an equal chance of landing with a marked or unmarked corner facing up. The number of marked ends facing upwards after a roll of the dice indicates how many spaces a player may move during that turn.
Players may choose to move any of their pieces on the board according to the dice score or add a new piece to the board if they have pieces yet to enter the game. A player is not required to capture a piece every time they have the opportunity. Nonetheless, players are required to move a piece whenever possible, even if it results in an unfavourable outcome.
All surviving gameboards have a coloured rosette in the middle of the centre row. According to Finkel's reconstruction, if a piece is located on the space with the rosette, it is safe from capture. Finkel also states that when a piece lands on any of the three rosettes, the player gets an extra dice roll. To bear a piece off the board, a player must roll the exact number of spaces remaining to the end of the course plus one. If the dice roll is higher or lower than the precise number, the player may not remove the piece from the board.
A single game may last up to half an hour. Elements of both luck and strategy are involved, so games can prove unpredictable and a close run thing at the end.