Knight Sacrifice on f5 • Caissa vs Starzix • 1st Godelia Computer Chess Tournament (2026) • French Defense: Tarrasch, Closed Variation (C05)
Francisco Yepes Barrera
3 min read
Immo Wegmann - https://unsplash.com/photos/a-close-up-of-a-chess-set-on-a-table-ISy8BdloKRo
This matchup brings us into the realm of modern silicon warfare, featuring a clash from the Godelia Computer Chess Tournament 2025.
Caissa 1.23 BMI2 is a sophisticated chess engine known for its aggressive positional understanding. Versions of Caissa are frequently updated to take advantage of specific CPU instruction sets (like BMI2), allowing it to calculate millions of nodes per second with surgical precision. Caissa is a high-performance chess engine written in C++. It is widely respected in the computer chess community for its robust positional play and efficient implementation of NNUE (Efficiently Updatable Neural Networks).
Michał Witanowski (Witek902), the creator, has optimized Caissa to take full advantage of modern CPU architectures. The engine features specific builds for BMI2 and AVX2 instruction sets, which significantly boost node-per-second (NPS) performance during deep searches. It is a frequent top-contender in major leagues like the TCEC (Top Chess Engine Championship).
Starzix is a formidable competitor in the engine circuit. Like many modern engines, Starzix utilizes neural networks to evaluate positions, often leading to a “human-like” but flawless defensive technique. The author is zzzzz151.
The Godelia Computer Chess Tournament is a high-level digital event hosted on Godelia.org. This tournament is initiated for testing the stronger chess engines. The time control, 40 moves in 300 seconds plus a 5-second increment, is designed to be fast enough to prevent total calculation of the game tree but long enough to allow for deep strategic planning.
This game is a theoretical battle in the French Defense, Tarrasch Variation (3. Nd2). It showcases White’s ability to maintain a persistent “plus” through space and pressure on the King.
The game started with 1. d4 e6 2. e4 d5 3. Nd2 Nf6. Starzix opted for a slightly unusual path with 9… b5, moving out of established book theory. Caissa responded logically with 10. a3, beginning a long-term plan to squeeze the Black position.
By the middle game, Caissa had established a classic French structural advantage. The move 19. h5 followed by 22. h6 created permanent weaknesses in the Black Kingside. Starzix tried to find counterplay on the queenside and the c-file, but the coordination of White’s pieces—specifically the Queen on g4 and the Knight on h5—kept Black paralyzed.
The evaluation began to climb significantly in White’s favor after 32. Bg5. Black struggled to find a way to activate the Bishop on c7.
The decisive moment came with the sacrifice 39. Nhf5!. White gave up a Knight to shatter the Black pawn structure. After 40. Nxf5 Kh8 41. Nh6, White’s attack became irresistible. Caissa used a series of checks and maneuvers to win back material and enter a winning endgame.
By move 58, the position was technically winning for White. Some small imprecision in this phase by Caissa doesn’t change the result. The game ended in an adjudication, as the engine scores reached a threshold where the result was no longer in doubt.
The game shows how to use a space advantage: Caissa used the e5 and h6 pawns to limit Starzix’s piece mobility throughout the entire game. Remarkable is the neural precision, i.e., the Caissa ability to transition from a long-term positional squeeze into a sharp tactical finish. The Nhf5 sacrifice is a classic example of “dynamic compensation,” where the structural damage to the King is worth more than the piece itself.
