The players were given two minutes per turn to make decisions and give orders.Parkin (2019). A Game of Birds and Wolves, chpt. 11: "Players were given two minutes in which to submit their orders for the next ‘turn’, to replicate the urgency of a real battlefield." The players issued their orders for their imaginary ships on pieces of paper that they passed to the Wrens—this prevented their opponents on the other side of the room from overhearing. The Wrens would then get down on the floor and compute the outcomes of the players' orders, drawing the trajectories of the ships in chalk. Roberts provided the Wrens with the performance characteristics of all ships concerned: the range of the U-boat's torpedoes, the speed of the ships, their turn speed, the precise capabilities of the escorts' sonar (then known as ASDIC), how engine noise might distort listening attempts, visibility at night, etc.
