The Siryk Variation was a tactic used in three-dimensional chess, developed by the Vulcan Grand Master Siryk in the 19th century. It was a conservative approach which created an interwoven pattern of strong and weak pieces, which created a near impenetrable defense that did not permit much leeway for a sudden offense. In 2269, after the Talin incident, James T. Kirk uses the principles of the Siryk Variations, which he had learned from Spock, while working as a cargomaster at Intrator II, arranging and balancing high- and low-mass modules within a freighter's hold. (TOS novel: Prime Directive)