The phrase refers to the relentless, aggressive nature of the game, which is one of the most famous "miniatures" in chess history, ending in a stunning double-rook sacrifice and a smothered mate in just 11 moves. The Famous Game (Reti vs. Tartakower, 1910)
: Reti (playing White) sacrificed his Queen to force Tartakowerās King into a position where it was checkmated by a double check from a Bishop and a Rook. The PGN (Portable Game Notation) Unmitigated Pugnacity.pgn
If you are looking for the text to use in a chess engine or viewer, here is the PGN for that specific game: The phrase refers to the relentless, aggressive nature