Rong Jinzhen and Liseiwicz co-created mathematical chess, a demanding game that transformed their teacher–pupil relationship into a close friendship and gave their shared intellectual work a lasting reputation. Its design made control, cooperation, and opposition difficult to separate: players planned their own campaigns while also taking charge of pieces positioned by an opponent. Though the game later circulated under Liseiwicz’s name, Rong Jinzhen had helped create it, and the story of its authorship became as consequential as its rules.

From Chess Partners to Collaborators

The game grew out of Liseiwicz and Rong Jinzhen’s habit of playing chess together. They became close friends, moving beyond the ordinary teacher–pupil relationship to spend time walking and eating together. Rong Jinzhen had previously stayed mostly at home during school holidays; as their chess partnership developed, he was away more often. At first, his family assumed he was simply playing chess with Liseiwicz. They later learned that the two were using their time to devise a new game.

Rong Jinzhen explained that Liseiwicz was such a strong chess player that he himself had little hope of winning. The imbalance discouraged him from continuing to play. Their response was not to abandon the contest but to redesign it: they wanted a game in which they would start on equal terms, without one player’s greater familiarity with established variations deciding the outcome. In their conception, victory would depend on intelligence.

A Board Built Around Two Kinds of Control

Mathematical chess used a board about the size of a desktop, with two military-style camps: one shaped like a hatch and the other like a Coptic cross. Rather than conventional chessmen, the players used mahjong tiles. Four routes crossed the board, with each player controlling two. The hatch camp had a fixed arrangement for its pieces, while the pieces in the Coptic-cross camp could start in positions chosen by the opponent. The opponent arranged them according to their own strategic purposes; once play began, each player took control of the pieces placed against them.

This reversal gave the game its characteristic strategic tension. A player had to move disadvantageously placed pieces toward positions that served their own plan, while also advancing pieces along the routes they controlled. Pieces could pass between the two camps, but the conditions for moving into the opposing camp at the same time were strict and demanded preparation. Movement rules changed with a piece’s location: pieces in the hatch camp could neither move diagonally nor jump over other pieces, while both moves were permitted in the Coptic-cross camp.

The game therefore required attention to several interlocking problems rather than a single line of attack. Players had to prepare their own pieces for intended moves, improve the positions of pieces initially arranged by an adversary, and anticipate the moment when both sides could move into the enemy camp simultaneously. The board made each player contend with an opponent’s plans and with the consequences of their own control over the opponent’s pieces. The result was not simply a contest between two armies, but a structure in which each player also had to work against the other’s arrangement of their forces.

Intelligence as the Game’s Subject

Liseiwicz described the game as complicated enough that most people could not play it, and said it had been designed for mathematicians. Its complexity lay not only in the number of rules but in how a player’s decisions changed the structure of the contest. The narrator understood its central paradox as a battle in which each commander had the opposing army under their command. The game could thus be understood as one contest between two players and, at the same time, as two further contests in which each player had to manage the effects of their own decisions.

For Liseiwicz, this structure made the game more than a recreation. He presented it as the outcome of research in pure mathematics and as a challenge to the limits of intelligence: the player’s subjective decisions could transform the organization of the game itself. His account led the narrator to wonder whether the game might be connected to his research on artificial intelligence. Rong Jinzhen, however, said he knew nothing about such research and believed Liseiwicz was not working on it. When asked why, he did not offer an explanation in the cited account. The narrator’s suspicion and Rong Jinzhen’s answer remain distinct perspectives rather than a settled account of the game’s purpose.

Rong Jinzhen gave a modest estimate of his own role. He said that he designed the board, while Liseiwicz worked out the rules governing how the pieces could move; asked to assess his share, he put it at about ten per cent. That estimate coexists with the narrator’s broader recognition that he had made a significant contribution. The game arose from a problem the two shared—the unequal footing of their original chess matches—and took shape through complementary work on its board and rules.

Reception and the Problem of Credit

The game became influential among mathematicians in Europe and America, where many people played it. It was no longer called mathematical chess: it took Liseiwicz’s name. Articles about it compared its theoretical importance with von Neumann’s theory of chess as a two-person zero-sum game. The comparison distinguished their proposed significance: von Neumann’s concept was associated particularly with economic theory, while Liseiwicz chess was regarded as potentially important to military strategy. The practical applications of both remained unproven, but their theoretical importance was considered substantial.

Liseiwicz was celebrated as the youngest recipient of the Fields Medal and as an ornament to mathematics. Yet after going to China, he produced little original research of comparable importance apart from the game, which became the last great achievement of his later career. That recognition came with an imbalance: once the game bore Liseiwicz’s name, Rong Jinzhen’s part in creating it had little chance of being acknowledged, and the public account of its authorship centered on Liseiwicz. The narrator holds this unfairness alongside evidence of genuine affection and Liseiwicz’s efforts to advance Rong Jinzhen’s future. Their collaboration therefore leaves two legacies at once: a mathematically ambitious game and a quieter history of shared invention whose credit was not shared equally.