Autumn Challenge 2026: Carlsbad – 4 New Weapons for Black
Four authors. One structure. Four different answers.
Few positions have been studied as deeply as the Carlsbad. After 1.d4 d5 2.c4 e6 3.Nc3 Nf6 4.cxd5 exd5 5.Bg5, White's plans have been known for more than a century: the minority attack with b4-b5, or f3 followed by e4.
That is exactly what makes it a hard test. When everyone knows the plans, Black needs more than general understanding. Black needs a concrete repertoire.
This database is the next stage of the Modern Chess Autumn Challenge. For this stage, GM Tomás Sosa, FM Sebastian Reimann, GM Jan Subelj and IM Ajay Santhosh received the same task: a repertoire for Black against the Exchange Variation with 5.Bg5. Each of them worked on it independently.
Four recommendations. No two alike.
The author who refuses to play ...c6
Three of the four authors answer 5.Bg5 with 5...c6, the classical move that prepares ...Bf5. FM Sebastian Reimann goes his own way:
"Instead of going for something solid and positional, my idea is to play concretely and go for a more fighting approach."
His answer is 5...Bb4!?. Black pins the knight at once and follows up with ...h6 and ...g5 in many lines.
Against the main line 6.e3 h6 7.Bh4 g5 8.Bg3, he does not choose the popular 8...Ne4, which has around 800 games behind it. He goes for the much rarer 8...h5!?, delaying ...Ne4 and hinting at ...h4 first.
Four solutions to the same problem
This database does not give you one author's taste. It lets you compare, and then choose:
- Sosa – 5...c6 6.e3 Qb6!?: Black unpins immediately, eyes b2 and fights for the initiative. After 7.Qc2 Ne4!, Black is ready to give material if it stops White's usual development. The system is rare, with around 500 games in the database.
- Reimann – 5...Bb4!?: the concrete approach, with ...h6, ...g5 and, in the main line, 8...h5!?
- Subelj – 6.e3 Be7 7.Bd3 Nbd7: the classical setup with a twist. Castling is delayed so the knight can go ...Nf8-e6, and Black's main strategic goal is exchanging the light-squared bishops.
- Ajay – an early ...h6 in every line: after 6.e3 h6 7.Bh4 Be7 8.Bd3 O-O 9.Nge2, he plays 9...Ne8!?, a regrouping that can be quite annoying for White.
Against 5...c6, White can also choose the 6.Qc2 move order, which avoids ...Bf5 altogether. Sosa answers with 6...Na6, making use of the early queen move with ...Nb4 in mind. Ajay plays 6...h6 7.Bh4 g6!?, so that ...Bf5 comes with tempo against the queen.
Where the authors meet: the knight on d6
The authors worked separately, yet a common idea keeps coming back: the black knight on d6.
In the Carlsbad, d6 is often the ideal square for Black's knight. From there it controls e4 and slows down White's f3-e4 plan, covers b5 against the minority attack, and eyes c4 and f5.
Ajay reaches it directly with ...Ne8-d6. Subelj names d6 as the best square for Black's knight in the structure. Sosa heads there in his endgame lines. He also adds a set of model games on the theme, including Bobotsov–Petrosian (1968) and
Portisch–Kasparov (1989).
When separate authors arrive at the same piece placement, it is worth understanding why. This database shows you each of their routes.
Why this format teaches more than a single repertoire
A conventional opening course gives you one answer and asks you to trust it. This one gives you four, each with the reasoning behind it.
The first benefit is choice. You can pick the treatment that fits your style: Reimann's sharp ...g5 lines, Sosa's early queen move, or the more classical setups of Subelj and Ajay.
The second benefit is less obvious. Seeing the same structure handled four ways teaches the structure itself. You understand what Black is really fighting for in the Carlsbad, not just which moves to play.
For anyone who faces 1.d4
The Exchange Variation with 5.Bg5 is one of White's most respected ways to meet the Queen's Gambit Declined. It is common at every level, from club games to elite practice.
Many players meet it passively and spend the game waiting for the minority attack. This database gives you four prepared answers from strong players who were competing to produce the best one.
Compare. Understand. Choose your answer.