A team of researchers from MIT, Carnegie Mellon, Stanford, and New York University has created an AI called Ataraxos, which has outperformed the best human players in Stratego, a complex board game known for its hidden information and a vast number of possible setups. The AI faced off against Pim Niemeijer, a four-time world champion and a well-known figure in the game, in July 2025. In a series of twenty games, Ataraxos won fifteen, lost only once, and drew four times. The findings of this research were published in the October 1, 2026, issue of Nature. Stratego poses a unique challenge for AI systems due to its reliance on hidden information and the massive number of possible arrangements for the game pieces, which exceeds 10^33. Unlike games where all information is visible, Stratego requires players to estimate what might be hidden behind their opponent's pieces, assign probabilities to various scenarios, and make decisions based on those estimates. Every time a piece is revealed, it provides new data that helps refine the AI's understanding of the opponent's strategy. DeepMind had previously made notable progress in 2022 with DeepNash, an AI that reached an expert level and entered the top three on the Gravon platform. However, DeepNash had not shown the same level of dominance over human elite players as Ataraxos. The training of Ataraxos is based on self-play, with an additional research phase when selecting a move. The system attempts to guess the identity of hidden pieces before considering different possible actions. Based on equipment rental costs in 2025, a full training session for Ataraxos would have cost less than $8,000, compared to several million dollars for DeepNash. Stratego now joins a list of games where AI has surpassed human expertise. In 1997, Deep Blue defeated Garry Kasparov in chess. In 2016, AlphaGo beat Lee Sedol 4-1 in the game of Go. In 2017, Libratus outplayed four top poker players, and Pluribus extended this success to six-player Texas Hold'em games. The remaining challenges for AI involve games with incomplete information and complex human interactions that are hard to translate into simple rules. For example, Bridge has not yet been fully conquered by AI, although an AI did beat world champions in a simplified version of the game in 2022. Similarly, Diplomacy, a game of negotiation and strategy, still presents challenges. Cicero, developed by Meta, reached the top 10% of players in an online league but was still considered human-level rather than clearly superior to human experts. With Stratego now conquered by AI, the list of areas where humans maintain a clear advantage over machines is shrinking significantly.