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What do you think is the most complex opening or variation there is?

#1

What do you think is the most complex opening or variation there is?

What do you think is the most complex opening or variation there is?
#2

These days, the question has lost its relevance due to the depth of engine analysis.
Take a look at Suleymanli v Karthikeyan from the Grand Swiss today where White played a queen sacrifice. Afterwards, Suleymanli said practically the whole game was his preparation.

These days, the question has lost its relevance due to the depth of engine analysis. Take a look at Suleymanli v Karthikeyan from the Grand Swiss today where White played a queen sacrifice. Afterwards, Suleymanli said practically the whole game was his preparation.
#3

Well, we can say that any opening where Black delays striking out in the center, such a just about any open Sicilian, Pirc, and also the King's Indian, will give White many options, and the opening tree can get very thick. So I guess these are complex openings. If I had to pick one, it would be the King's Indian Defence. The highly regarded "Kotronias on the King's Indian", a repertoire series for Black, runs five volumes and over 1500 pages.

Well, we can say that any opening where Black delays striking out in the center, such a just about any open Sicilian, Pirc, and also the King's Indian, will give White many options, and the opening tree can get very thick. So I guess these are complex openings. If I had to pick one, it would be the King's Indian Defence. The highly regarded "Kotronias on the King's Indian", a repertoire series for Black, runs five volumes and over 1500 pages.
#4

The question of complexity depends on the number of moves considered. It also depends on the number of nodes.
To compare different openings, we must agree on a consistent number of moves or nodes.

Example:
For one-move openings, I believe the Sicilian Defense is the most complex.
For two move openings, go ahead find the answer ...
For 3-movers, ...
4-movers ...

https://arxiv.org/html/2505.03251
https://github.com/tromp/ChessPositionRanking

The question of complexity depends on the number of moves considered. It also depends on the number of nodes. To compare different openings, we must agree on a consistent number of moves or nodes. Example: For one-move openings, I believe the Sicilian Defense is the most complex. For two move openings, go ahead find the answer ... For 3-movers, ... 4-movers ... https://arxiv.org/html/2505.03251 https://github.com/tromp/ChessPositionRanking
#6

When an opening is complex the analysis of every pv line is similar. When you pick a pv line you will have to have a strategy. Sometimes even the following choice is not clear if the prior move was tactically sound.

https://lichess.org/analysis/pgn/e4_c5_Nf3_d6_d4_cxd4_Nxd4_Nf6_Nc3_a6_Bg5_e6

When an opening is complex the analysis of every pv line is similar. When you pick a pv line you will have to have a strategy. Sometimes even the following choice is not clear if the prior move was tactically sound. https://lichess.org/analysis/pgn/e4_c5_Nf3_d6_d4_cxd4_Nxd4_Nf6_Nc3_a6_Bg5_e6
#7

Grox Strategy for Choosing a PV that aligns with style:

Aggressive? Pick PV1 (7.f4) for f5-based attacks; requires tactical precision.
Positional? PV2/PV3 (7.f3 or 7.Qd2) for flexible O-O-O setups.
Risk-averse? PV4 (7.Qf3) or PV5 (7.Be2) for simpler, balanced positions.

Grox Recommendation:

Best PV: PV1 (7.f4) for its slight edge and attacking chances, but only if you’re comfortable with sharp tactics. PV3 (7.Qd2) is a solid alternative for flexibility.

Next Steps: Play through PV1 and PV3 on Lichess’s analysis board, testing sidelines (e.g., 8...g5 in PV1 or 9...Nbd7 in PV3). If a specific move or subline confuses you, share it for deeper analysis!

Grox Strategy for Choosing a PV that aligns with style: Aggressive? Pick PV1 (7.f4) for f5-based attacks; requires tactical precision. Positional? PV2/PV3 (7.f3 or 7.Qd2) for flexible O-O-O setups. Risk-averse? PV4 (7.Qf3) or PV5 (7.Be2) for simpler, balanced positions. Grox Recommendation: Best PV: PV1 (7.f4) for its slight edge and attacking chances, but only if you’re comfortable with sharp tactics. PV3 (7.Qd2) is a solid alternative for flexibility. Next Steps: Play through PV1 and PV3 on Lichess’s analysis board, testing sidelines (e.g., 8...g5 in PV1 or 9...Nbd7 in PV3). If a specific move or subline confuses you, share it for deeper analysis!
#8

Picking a PV line requires having a strategy in place.
FEN: rnbqkb1r/1p3ppp/p2ppn2/6B1/3NP3/2N5/PPP2PPP/R2QKB1R w KQkq - 0 7

Lichess Cloud evaluation SF 17.1 NNUE 79MB @ depth 55
PV1 +0.2 cp 7. f4 h6 8. Bh4 Qb6 9. a3 Nc6 10. Bf2 Qc7 11. Qf3 e5
PV2 0.0 cp 7. f3 b5 8. Qd2 Be7 9. O-O-O h6 10. Be3 b4 11. Na4 Qa5
PV3 0.0 cp 7. Qd2 Be7 8. f3 b5 9. O-O-O h6 10. Be3 b4 11. Na4 Qa5
PV4 0.0 cp 7. Qf3 Nbd7 8. Be2 Qc7 9. a4 b6 10. O-O Be7 11. Rad1 O-O
PV5 0.0 cp 7. Be2 Be7 8. O-O O-O 9. a4 d5 10. exd5 Nxd5 11. Bxe7 Nxe7

Picking a PV line requires having a strategy in place. FEN: rnbqkb1r/1p3ppp/p2ppn2/6B1/3NP3/2N5/PPP2PPP/R2QKB1R w KQkq - 0 7 Lichess Cloud evaluation SF 17.1 NNUE 79MB @ depth 55 PV1 +0.2 cp 7. f4 h6 8. Bh4 Qb6 9. a3 Nc6 10. Bf2 Qc7 11. Qf3 e5 PV2 0.0 cp 7. f3 b5 8. Qd2 Be7 9. O-O-O h6 10. Be3 b4 11. Na4 Qa5 PV3 0.0 cp 7. Qd2 Be7 8. f3 b5 9. O-O-O h6 10. Be3 b4 11. Na4 Qa5 PV4 0.0 cp 7. Qf3 Nbd7 8. Be2 Qc7 9. a4 b6 10. O-O Be7 11. Rad1 O-O PV5 0.0 cp 7. Be2 Be7 8. O-O O-O 9. a4 d5 10. exd5 Nxd5 11. Bxe7 Nxe7
#9

Depends on what you mean by complex. If you mean simply the size of the tree. sure probably the Sicilian But that tree gets pruned quickly, by Black. If you want to speak in practical terms, I still say a King's Indian repertoire is far more complex than a Sicilian repertoire. Just ask Garry Kasparov, who forsook the KID in favor of the QGD, but kept the Sicilian, because of the amoubt of work involved.

Depends on what you mean by complex. If you mean simply the size of the tree. sure probably the Sicilian But that tree gets pruned quickly, by Black. If you want to speak in practical terms, I still say a King's Indian repertoire is far more complex than a Sicilian repertoire. Just ask Garry Kasparov, who forsook the KID in favor of the QGD, but kept the Sicilian, because of the amoubt of work involved.
#10

The Chess Book Grandmaster Preperation by Lev Poulgevesky looks at The Variation ... the Poulgevesky Variation in The Najdorf & the work at his "Lab" Poulgavesky had to go through in order to play it at the highest levels . He also has a book called Grandmaster Performance which investigates many different aspects of tournament play . Both books are by Pergamon Chess

The Chess Book Grandmaster Preperation by Lev Poulgevesky looks at The Variation ... the Poulgevesky Variation in The Najdorf & the work at his "Lab" Poulgavesky had to go through in order to play it at the highest levels . He also has a book called Grandmaster Performance which investigates many different aspects of tournament play . Both books are by Pergamon Chess

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