The 9...a5 Move Against the Bayonet Attack: A Clean Remedy, or a Skillful Sales Pitch?

Late one night, during an online analysis session, I stopped at the ninth move of a game between two players nearly 200 Elo apart. White pushed the pawn to b4 — the familiar Bayonet Attack — and the chat erupted: "That's it, Black is about to get hanged." Ten minutes later, Black played a5. No hesitation, no long calculation. The game ran another sixty moves, and White — the higher-rated side — salvaged only a labored draw. I wrote a5 into my notebook. Three weeks later, I came across an opening product advertising exactly that move as a "clean remedy" for the King's Indian Defense. My professional instinct kicked in: when the seller grades his own product, the buyer must re-grade it himself. To see why a5 deserves time, the position must be rebuilt from the start. White plays d4, Black answers Nf6; White c4, Black g6; White Nc3, Black Bg7; White e4, Black d6; White Nf3, Black castles; White Be2, Black e5; White castles, Black Nc6. This is the Mar del Plata variation, born from the tournament of the same name in 2026. White pushes d5, Black retreats Ne7, then White b4 — the Bayonet Attack, the pawn thrust the theory community considers White's most ambitious try. Black replies with a5. The Bayonet Attack is no idle pastime. At the top level, it is the choice leading players use to avoid Mar del Plata lines that have been dissected to the bone. When White picks b4, White is telling Black: I do not want to play by your book. Black answering with a5 answers in the language of the position, not the language of the variation table. In the King's Indian system, Black voluntarily cedes the center and strikes back with e5 and c5. The Mar del Plata is the sharpest branch: after White builds the Classical setup, Black brings the knight to c6 to pressure d4. The Bayonet Attack emerged as a direct counter — White opens the queenside front, pushes b4 and eyes b5, aiming to gouge Black's pawn structure before Black can counterattack. Black's orthodox theory here is 9...Nh5. That is the highway: the position opens up, the lines turn forcing, and the computer becomes the arbiter again. The 9...a5 goes another way — striking directly at the advanced b4-pawn, grabbing queenside space, and accepting a strategic battle instead of a calculation race. This is the distinction the opening product leans on to position itself. The product advertises a5 with three claims: the position is sound, the chances are equal, and there are few concrete lines. All three come from the seller. There is no win-draw-loss table, no engine match rate, no game sample. This is the first thing I mark in red. In my own analysis, I always start with three metrics: engine match rate, average centipawn loss per move, and the win-draw-loss rate in a database. For a5, all three are empty. This does not mean the line is weak. It means no one has proven it strong through an independent route. In that void, the seller has full freedom to tell his story. Let us separate the issues. a5 is a known sideline, not a novelty. It has been used to strike directly at the b4-pawn, and it still sits within the ECO E97–E99 family of the Bayonet. So the word "remedy" here is relative — a legitimate alternative, not an overthrow. The seller is not lying, but the seller chooses the framing that favors him. The "few concrete lines" claim has real value. Low forcing density means fewer calculation traps, less risk of falling into a prepared ambush. But this is a double-edged sword. The same feature that makes the position low-risk also makes it unforgiving: the player must understand the plans, not memorize a move sequence. I recall a lesson from a Chinese club in 2026, when I analyzed the performance of a Brazilian striker for a team in Tianjin. He scored 22 goals in the national league, a beautiful set of numbers. But when I broke down expected goals and touches inside the box, his real efficiency was 18 percent below expectation, mostly from set pieces. The pretty chart hid a predictable attacking system. It took me three months to learn that a beautiful chart is no match for a correct process. And a Chinese club taught me that data is not the destination, but a walking stick. That applies directly to a5. A "clean" opening line does not mean a stronger one. It only means fewer forced moves. To know whether it is truly equal, I need independent data: game counts in a database, Black's win-draw-loss rate, and a cross-check against modern engines. The seller does not offer those. So I go looking myself. One small but telling detail: the author himself concedes that "objectively, the chances are equal." This is the familiar credibility hedge of serious opening authors. They do not promise a forced advantage; they promise a playable position. A wise buyer should take that concession more seriously than any flashy marketing line. Strategically, a5 strikes right at the Bayonet's weak point: the b4-pawn advances far but lacks support. Black forces White to decide immediately — hold b4 with a3 or b5, or let it hang. Each choice opens a different structure, and each structure demands a long-term plan. This is the kind of position where the player who understands the position beats the player who parrots moves. By classification, a5 belongs to the secondary sidelines of the King's Indian. Its theoretical footprint is smaller than Nh5, meaning less to memorize but also less refinement. Its practical value lies in surprise: opponents prepare for a5 far less than for Nh5. But surprise value is cyclical. When the Bayonet reigns at the top level, sidelines like a5 rise in value. When the Bayonet fades, they cool off. The line's true arena is not elite closed events. It is open tournaments and team matches, where the Bayonet appears far more often than at elite events. There, the surprise value of a5 is tested every week. And there, too, strategic errors are punished fastest, because the opponent does not need to play perfectly — only patiently. The target buyer profile is also worth discussing. This product aims at club-to-master players — roughly 1800 to 2400 Elo — who cannot maintain their own engine-backed opening database. Leading grandmasters do not need this product; they already have their own systems. The absence of any endorsement from a top player says as much: this is a general-purpose tool, not documentation of a star's pet line. On distribution, the DVD format suggests a traditional publishing channel that is shrinking but durable, now competing with subscription repertoires. The product's strength lies in the "understand over memorize" segment — a real but smaller market than main-line repertoires. Sales of such products tend to spike when the Bayonet reigns at the top level, making their life cycle cyclical with opening fashion. Here I must contradict myself. The thing that bothers me most in the advertising is the claim that "computers do not know how to handle these positions." That is a familiar marketing trope of every opening product. Modern engines handle the Mar del Plata positions of the King's Indian very well. The author himself concedes that in the main Nh5 line, "computer analysis becomes important again" — a remark that inadvertently refutes his own earlier claim. The truth lies elsewhere. a5 does not confuse the computer. a5 confuses the player less, because it has fewer forcing moves. That is the difference between "the computer does not understand" and "the human has less to calculate." Blending the two is an appealing packaging trick, but not a technical fact. Then comes the correlation-versus-causation trap. It is easy to read "a5 leads to equality" as a causal relation. But equality in sample games may come from White opponents playing inaccurately, not from the intrinsic strength of a5. Without a large sample and a control group, every conclusion is just a dressed-up guess. And there is a paradox of time. The whole appeal of a5 lies in rewarding calm, strategic play. But those very slow plans are most easily punished in rapid and blitz, when the player has no time to calculate long-term plans. An opening line sold as a "lifeline" can be a weakness in exactly the format most buyers play. I once believed absolutely in numbers. In 2026, based on possession data and passing accuracy in the qualifiers, I predicted a strong national team would defend its title. They were eliminated in the group stage. The data was not wrong — I had ignored the metrics that were not in my spreadsheet. After that shock, I spent three weeks rewatching the entire group stage, learning to measure field tilt and high turnovers. I no longer trust single predictions. I trust only early-warning systems. So with a5, I do not rush to a conclusion. I put it on a watchlist, with three signals to observe: the frequency of the Bayonet at elite events, new engine analysis of the a5 line itself, and independent win-draw-loss statistics for Black in this line. When data does not lie, it is we who deceive ourselves. The buyer of that product may find a useful tool. What they must remember is that it is a practical tool for a player who understands the position, not a theoretical revolution. If you intend to buy, buy because you want to understand, not because you want to memorize. And if all you want is one move to get through the opening — check yourself before you check your opponent.