9...a5 and the Bayonet Problem: A Strategic Shield in the King's Indian

Black's clock read 38 seconds when White pushed b4. The ninth move was the Bayonet, that familiar strike at the queenside in the King's Indian, the one every Black player in this system has seen on an analysis screen. Black did not touch a piece for fourteen seconds. Then …a5 appeared, a quiet move placed exactly where White had just expanded.

Fourteen seconds — enough to redraw the opponent's entire defensive map. In those fourteen seconds, Black was not calculating. Black was choosing a map: either the theoretical motorway with …Nh5, where everything has been pushed to move 28 by the engine, or a direct strike at the b4 pawn, accepting a position with few forced sequences but a great deal of space to read.

The opening product I received this week chooses the second path. It is advertised in one short line: a clear answer to the Bayonet. I read the pitch three times, and on the third pass I stopped at the sentence where the author concedes that, objectively, the chances are equal. That is the most important line in the entire advertisement, and it is the only one that is not bolded.

Context: the move order and the price of a pitch

The whole story fits into two lines: 1.d4 Nf6 2.c4 g6 3.Nc3 Bg7 4.e4 d6 5.Nf3 0-0 6.Be2 e5 7.0-0 Nc6 8.d5 Ne7 9.b4. This is the Classical King's Indian, and the seventh move …Nc6 takes the game into the Mar del Plata variation, named after the 2026 tournament in Argentina where the system was first dissected at the highest level. In ECO terms, the whole complex sits in the E97 to E99 range.

The move 9.b4 is White's most ambitious try. White does not fight for the centre by trading; White expands on the queenside, pushes b4 and then b5, and squeezes Black's space on the side Black has already conceded. For White, the Bayonet is a declaration that the game will be decided by space, not by a quick counterattack.

Black's mainstream answer is 9...Nh5, and this is the anchor of every textbook. After …Nh5 the position opens, the lines become forced, and — in the author's own words — computer analysis becomes important again. In other words, …Nh5 is a road both sides must memorise, and whoever forgets first loses first.

This product sells a different road: 9...a5. The author's case is compact — the resulting positions are sound, the number of concrete forced lines is very small, and the focus is on strategy rather than tactics. That is a coherent argument. But it must be said at the outset: every flattering adjective in that paragraph was written by the seller. No independent database is cited, no win-draw rate, no ACPL, no engine match rate. In my trade, a claim without numbers is a hypothesis waiting to be tested.

The core: what …a5 does on the spatial map

The move 9...a5 has a very clear mechanical job. White's b4 pawn has just left its starting rank, which means it has just become a target. …a5 strikes at that target directly, opens the a-file for the rook, and creates the possibility of …axb4 followed by …c5 or …a4 depending on White's response. White has several ways to handle it: trade immediately on a5 to clear the queenside, keep the tension with Ba3 or Be3, or push b5 to lock the space. Each choice leads to a different map, and that is precisely why …a5 is not a move but a family of positions.

This is where its place in the theoretical landscape becomes visible. …Nh5 turns the game into a calculation race: whoever remembers deeper, whoever updated their engine file more recently. …a5 turns it into a reading contest: whoever understands the structure better wins. These are two different sports played on the same board.

The real value of 9...a5 is not the word 'answer' — it is that the move converts a theory game into a plan game. For a club player between 1800 and 2400, exactly the segment this kind of product targets, that conversion is worth far more than memorising thirty more moves of a main line the opponent has already prepared.

But the price of that conversion is equally clear. Low forcing density means Black has fewer handholds. In a …Nh5 line, if you forget move 22, you lose a pawn and may survive. In an …a5 structure, if you misread the plan, you lose nothing immediately — you are simply half a tempo behind for fifteen moves in a row, and by move fifteen there is nothing left to save. The spatial map never lies; it only exposes what we want to believe.

That is also why I always check the time-control variable when assessing products like this. A strategic, low-forcing position is a gift in classical chess and a trap in blitz. With five minutes on the clock for both sides, a player needs automatic moves, not plans that require three minutes of thought. The author does not mention this, and it is a notable gap in a pitch aimed at practical players.

At the club where I play on Tuesday nights in Chiang Mai, I tried recording the group's reactions when this position came up. Four players took Black. Three played …Nh5 by reflex, even though none of them could recall past move fourteen of the main line. One played …a5 and then grew visibly uncomfortable when White pushed b5 and switched to the kingside. The result says nothing about the theoretical value of either move, but it says something about players: we tend to choose the familiar road even when we lack the data to travel it.

The contrarian angle: what the engine doesn't understand, and what the player doesn't either

One sentence in the pitch stopped me for the longest: computers do not know how to handle these positions. That claim is false, and it is false systematically. Modern engines evaluate Mar del Plata structures very well — well enough that professional players use them as the benchmark for the very lines the author is selling. Worse, the author undermines his own case a paragraph earlier by saying that after …Nh5, computer analysis becomes important again. If engines did not understand the position, they would not matter on any branch.

The real blind spot is not the engine. It is that the product is sold on an argument of saving memorisation effort, while demanding considerably more understanding effort. The buyer who wants to avoid remembering will be the first to fail in a position with no forced lines, because with nothing to recall there is also nothing to cling to. A player who understands the structure will find …a5 comfortable. A player who memorises will find it empty.

And surprise value has an expiry date. The practical worth of …a5 depends on whether the Bayonet remains popular. When White plays 9.b4 regularly, sidelines like …a5 have room to live because opponents prepare less against them. When Bayonet frequency falls, the product loses half its reason to exist. This is the rule of the entire opening market: every answer has a shelf life, and the shelf life is decided by other people, not by the author.

What to carry into the next game

If I have to set one hypothesis for next week, it is this: in King's Indian games where Black chooses …a5, record when the move appears — before or after White completes queenside development. If …a5 comes early, with a clear queenside plan behind it, the position tilts toward the player who understands structure. If …a5 comes late, as a passive reaction after White has already pushed b5, it is merely a confession.

Every opening idea is a hypothesis until the pieces touch the board. And this hypothesis, like every other, will be verified not by a sales pitch, but by games in which someone sits across the board and has read no advertisement at all.