Mar del Plata 2026: The 9...a5 Move and the 'No Memorization Required' Promise

Hook

In March 2026, at the HDBank Cup in Ho Chi Minh City, I sat in the third row and watched a nineteen-year-old Vietnamese player think for forty-two minutes about move nine. At the next board, a foreign coach opened his notebook and stopped at a page marked "9.b4." Both men believed they were calculating. Both men were reciting.

The same week, an opening DVD went on sale in Europe with a very tidy pitch: the move 9...a5 is the antidote to the Bayonet Attack, and this antidote requires no memorization.

I pushed back immediately.

Context

The King's Indian Defense, Mar del Plata variation, is one of the few systems that has kept its personality in the computer age. The game runs: 1.d4 Nf6 2.c4 g6 3.Nc3 Bg7 4.e4 d6 5.Nf3 O-O 6.Be2 e5 7.O-O Nc6 8.d5 Ne7.

White pushes the pawn to d5, locks the centre, and accepts that Black will be squeezed into the back half of the board. The price Black pays for being squeezed is the right to choose where to counterattack. Black pushes ...f5 at the kingside. White pushes b4 and then b5 at the queenside. Each side races to break into the other's house, and neither can afford to lose a tempo.

The move 9.b4 — the Bayonet Attack, inside the ECO E97 group — is the fastest way for White to turn the queenside into a real front. It prepares b5, threatens Na4 followed by Nc5, and, more importantly, it forces Black to answer right now.

The answer taught in books for decades is 9...Nh5. Black puts the knight on the rim and prepares ...f5, ...Nf4 and ...g5. The position becomes tense at once, every move carries consequences, and both sides must calculate more than twenty moves deep. For a club-level player, this is a nightmare: one wrong move early is enough to lose before you understand what happened.

Back then I used to ask coaches at domestic events what their students had prepared against 9.b4. The question I asked did not sound like a woman's question, but the answers they dodged did not sound like men's answers either.

The DVD offered a different road: 9...a5.

In that silent hall, with no applause at all, I found the tactical diagram lying still on the scoresheet instead of the roar of a crowd.

Core

The move 9...a5 does not attack the centre, does not open the kingside, does not threaten mate. It touches exactly one thing — the b4 pawn that has just jumped.

The idea: if Black can trade with ...axb4 at the right moment, White's queenside turns from a building site into a repair site. If White wants to push b5, a4 must be prepared first; every preparatory move is a breath for Black. Black's rook gets the a-file. Black's knight gets the c4 square. And White, used to attacking, suddenly has to defend on the very wing it just claimed.

The core point: 9...a5 turns the game from a sprint into a negotiation. Black stops trying to score in the first thirty moves; Black lengthens the game, trades pieces, and waits for White to lose patience.

That sounds reasonable. But the pitch has three gaps, and all three sit in the part the seller does not mention.

The gap is that 9...a5 was never an invention. It has sat in databases for years, it is played in open tournaments, and any player above 2400 with serious preparation has met it at least once. The seller calls it an antidote. The books call it an option. Same move, two labels, and both labels sell.

The next doubtful point is the promise of "few concrete lines, little to remember." I have spent most of my career sitting in playing halls, and I have never seen anyone buy an exemption from calculation. 9...a5 does not erase calculation. It relocates it: from "what do I play here" to "when do I trade, with what, and who gets to open which file." That is still homework, only the long-form kind that is harder to grade. A mistake is not what frightens you; kneeling down at two in the morning to pick the footage back up is what makes a forecaster.

The biggest gap sits in the sentence every DVD seller used in 2026: computers cannot understand positions like this. It was a convenient sentence — if the machine does not understand, the buyer never has to check with the machine. But computers in 2026 handled long-term strategic positions better than humans in almost every phase of the game. What the machine could not do was explain. What the machine could not do was tell you why move seventeen mattered more than move twenty-three. That is human work — and it is precisely the work being charged for.

And there is one more blank space: the DVD names no author, cites no record by that author in the Mar del Plata itself, and shows no sample game. The buyer pays for a signature he never gets to see.

In Vietnam this story is not unfamiliar. Our chess culture teaches memory very well: juniors recite whole trees out to move thirty, and in domestic youth events that wins games. It also produces players who freeze when the opponent leaves the book. The leading Vietnamese players of that time — Le Quang Liem and Nguyen Ngoc Truong Son — understood this best: memory gets you into the playing hall, it does not win you the game there. 9...a5 hits exactly there. It does not ask what you remember. It asks what you understand.

Contrarian

Where can I be wrong?

There is one possibility I have to concede. 9...a5 may genuinely help, just not in the way it is advertised. If the buyer is an 1800 player drowning in ...Nh5 lines, then a system that lets him drag the game into a slow position with few traps is a bargain — not because it is stronger, but because it fits how he calculates. The best weapon is not the strongest weapon. The best weapon is the one your hand does not shake while holding.

My deepest suspicion is not about the move. It is about the seller. An opening product lives on two things: the author's credibility and the speed of updating when the opponent hits back. This DVD shows neither. It shows one slogan.

Silent applause can kill emotion, but it cannot kill tactics. A chess hall is already silent as paper, and inside that silence people still win with moves, not with pitches.

Takeaway

My prediction, and it is testable: within eighteen months, a second DVD will appear teaching White how to handle 9...a5. And there is a simpler check: open a database of elite games and filter for 9...a5. If after two years it still shows up only in open tournaments and games below 2500, then it is a beginner's tool, not a leader's weapon.