An AI method first tested in Stratego has now produced strong results in Stratego’s faster Barrage variant, the cooperative card game Hanabi and China’s team card game dou dizhu, according to a Nature paper published September 30. The researchers trained a separate system for each, testing whether the approach works across game types rather than whether one bot can play them all.
The paper’s best-known Stratego result is not new: the authors reported it in a November 2025 preprint. Their Ataraxos system beat four-time world champion Pim Niemeijer in a 20-game series, with 15 wins, one loss and four draws. The new study asks whether the approach can also work in games with different rules and social structures.
Stratego hides the rank of most opposing pieces. Ataraxos learns by playing itself, using a policy network to choose moves and a value network to estimate outcomes. A separate belief network predicts which hidden pieces could fit the information revealed so far. Ataraxos tests candidate moves in those possible layouts, then uses the simulated results to choose a move for the current position.
For Barrage Stratego, a faster variant, the paper reports that a separately trained system beat three multi-time world champions. In Hanabi, where players cooperate but cannot see their own cards, its systems reached state-of-the-art scores in two- to five-player versions. In dou dizhu, a three-player game in which two players team up against one, the authors report state-of-the-art performance against existing AI systems. For Hanabi, the paper reports 10,000 games per test condition; when every player used search, average scores ranged from 24.41 to 24.86 out of 25.
The 20-game Stratego series lasted three weeks, and its outcomes were not independent: Niemeijer could adapt to the AI, while the AI did not adapt to him. The additional tests use games with known rules and simulators, so they show that the method can work across several formal game settings, not that it is ready for decisions in markets, military planning or other real-world settings.
Photo by zizou man, Wikimedia Commons, licensed under CC BY 2.0. The image shows a Stratego game; it is illustrative and is not an Ataraxos match.