Flank Opening Deep Lines
The deep-line archive of Volume A: named sub-variations of the English, Réti, Bird's, Dutch, Benoni and Benko — the lines that decide real games once both players know the first ten moves.
Flank Opening Deep Lines is one of the most compelling entries in the Encyclopaedia of Chess Openings — and a line that repays every hour you sink into it.
After 1.c4 the position resolves into an open centre — the central pawns have largely been traded, so open files and piece activity decide the game rather than pawn play.
The moves
After 1. c4 — Flank Opening Deep Lines main line
Position breakdown
A factual read of the position after the main line — the files, the centre, the pawn structure and king safety that decide how the middlegame is played. These are computed from the actual board, not generic advice.
Files
Centre control
Open centre
The d4/d5/e4/e5 squares — who occupies the centre decides how open the game becomes.
Pawn skeleton
Pawns only — the structure that explains every open file and majority at a glance.
Material level
Queenside pawns 3–3
Kingside pawns 3–3
Development
No minor pieces developed yet
No minor pieces developed yet
King safety
White king e1
Uncastled — take care
Black king e8
Uncastled — take care
Computed from the final position of the main line above — 1 plies, black to move.
Strategic ideas
Ideas for White
Master the move-order subtleties: these lines transpose or diverge by a single tempo, and knowing which is which is preparation itself.
Ideas for Black
Pick one system per main opening and drill it deep — flank openings reward structure-masters over tacticians.
Main variations (75)
English, Symmetrical Hedgehog
A30The Hedgehog core: the a6-b6-d6-e6 chain versus the c4/d4 clamp.
English, Symmetrical d4 Main
A33The pin structure: Bb4 tension versus the d5 outpost.
English, King's English 4.d44.g3 Setup
A28The g3 fianchetto setup: the King's English's main treatment.
English, Reversed Dragon
A26The Reversed Dragon: the Yugoslav attack with an extra tempo.
English, Mikenas 3...c5 4.e5
A18The e5 wedge: the sharpest Mikenas continuation.
English, Agincourt d4
A13The full centre: transposing to QGD structures with Nc3 first.
English, Neo-Catalan b3
A14The b3/Bb2 build-up: the Catalan pressure via English move order.
English, Anglo-Indian d4
A16The d4 strike: transposing to QID/Nimzo structures at will.
English, ...c5 Hedgehog Setup
A35The double-fianchetto Hedgehog: mirrored flexibility.
English, Flohr-Mikenas d5
A18The ...d5 strike: the central counterattack against the Mikenas.
Réti, Accepted 3.e3 Setup
A09The e3 support: solid development before Bxc4 recapture.
Réti, Catalan Setup
A06The d4 strike: the full Catalan transposition from the Réti.
Réti, Nf3-c4Réti 2...c6 Setup
A11The Slav-style ...c6 support: solid, solid, solid.
Réti, King's Indian Attack Setup
A07The castling-first setup: the KIA's patient build-up.
KIA, ...c5 Strike Setup
A07The ...c5 strike: Black's queenside counterplay begins.
KIA, e5 Wedge Setup
A07The e5 wedge: maximum space in the KIA structure.
Bird, Lasker Setup
A02The Lasker setup: solid development in the Bird's structure.
Bird, Symmetrical Setup
A02The double-Bird: mirrored flank grabs.
Dutch, Leningrad ...Ne5
A88The ...Ne5 regrouping: the knight heads for the strong central point.
Dutch, Classical Qe8-h5
A96The queen raid: the classical Dutch attacking plan in full.
Dutch, Stonewall Bd6 Setup
A93The early ...Bd6: the Stonewall's attacking bishop placement.
Dutch, Staunton 5.f3 Main
A83The f3 strike: opening the position in the Staunton gambit.
Dutch, Classical Be7 Setup
A90The solid ...Be7 setup: the classical Dutch's flexible development.
Benoni, Czech Setup
A43The Czech Benoni: the closed structure with ...e5 space claims.
Benoni, Modern ...g6 Setup
A65The g6 setup: the Modern Benoni's fianchetto structure.
Benko, Accepted Main
A57The full acceptance: the Benko's signature structure.
Benko, 7.Nf3 Setup
A58The Nf3 development: the classical Benko battleground.
Budapest, Adler Main
A51The Adler: the solid knight-development answer to the Budapest.
Trompowsky, 2...Ne4 Main
A45The Bf4 retreat: the main anti-...Ne4 treatment.
Old Indian, Main Setup
A53The main Old Indian: solid development with the ...e5 claim.
Englund, 3.Nc3 Setup
A40The knight-development answer: heading for e4 and dxe5 consolidation.
Polish, 2...Bf5 Setup
A00The solid bishop development: the main Polish structure.
Grob, 2...c6 Setup
A00The ...c6 support: solid structure against the Grob.
Larsen, 1...e5 Main
A01The classical setup: full development against the Bb2 pressure.
English, Double Fianchetto Setup
A35The double-fianchetto structure: the first break decides.
English, ...d5 Strike
A30The ...d5 strike: the central counterattack against the Symmetrical.
English, Botvinnik a3 Setup
A26The Rb1 prophylaxis: the Botvinnik system's queenside preparation.
English, Four Knights d4
A29The d4 strike: the central release in the Four Knights English.
English, Keres ...d5 Strike
A23The Keres strike: the central counterattack at its best.
English, ...Nge7 Setup
A26The ...Nge7 setup: the Closed English's flexible regrouping.
English, ...Rb8 Setup
A37The ...Rb8 preparation: the queenside counterattack begins.
English, Bb2 Setup
A30The b3 build-up: the full double-fianchetto development.
English, ...Be7 Setup
A28The ...Be7 setup: solid development in the King's English.
Réti, ...e6 Setup
A06The ...e6 setup: maximum flexibility against the Réti.
Réti, ...Nf6 Setup
A05The ...Nf6 setup: the most popular Réti defence.
Réti, ...g6 Setup
A06The ...g6 setup: the Grünfeld-flavoured Réti defence.
KIA, Trojan e5 Setup
A07The Trojan e5 wedge: maximum space in the KIA.
KIA, Nbd2 Setup
A07The Nbd2 development: the KIA's standard regrouping.
Bird, Dutch Setup
A03The ...g6 setup: the fianchetto defence to the Bird's.
Bird, ...c5 Setup
A02The ...c5 strike: queenside counterplay against 1.f4.
Bird, From's Accepted
A02The From's acceptance: the sharpest Bird's battleground.
Dutch, Stonewall Setup
A92The Stonewall formation: the famous fortress structure.
Dutch, Ilyin-Genevsky Setup
A96The Qe8 setup: the romantic queen-march begins.
Dutch, Staunton Accepted
A82The full acceptance: the sharpest anti-Dutch battleground.
Benoni, Fianchetto Setup
A61The g3 setup: the positional Fianchetto Benoni.
Benoni, Classical Setup
A65The classical setup: the Modern Benoni's main structure.
Benoni, Taimanov Setup
A67The Bb5+ check: the Taimanov's signature pressure.
Old Indian, d5 Setup
A55The d5 clamp: the Old Indian's structural battleground.
Englund, Qe7 Setup
A40The ...Qe7 setup: the main Englund trap system.
Budapest, Fajarowicz Setup
A51The ...Ne4 leap: the spikiest Budapest branch.
Trompowsky, e6 Setup
A45The ...e6 setup: the solid answer to the Trompowsky.
Polish, 1...e5 Setup
A00The ...e5 strike: the central counter against 1.b4.
Grob, Main Setup
A00The Bg2 development: the Grob's main setup.
Larsen, 2...Nf6 Setup
A01The ...g6 setup: the fianchetto defence to the Larsen.
English, ...Nf6 Setup
A10The Anglo-Indian: the most popular English defence.
English, ...e6 Setup
A13The Agincourt: the flexible French-flavoured defence.
English, ...e5 Setup
A20The King's English: the reversed-Sicilian defence.
English, ...c5 Setup
A30The Symmetrical: the mirror defence to 1.c4.
Réti Setup
A04The pure Réti: the most flexible first move in chess.
Bird Setup
A02The Bird's: the kingside flank grab from move one.
Dutch Setup
A80The Dutch: the kingside-grabbing defence to 1.d4.
Benko Setup
A57The Benko strike: the queenside gambit at its purest.
Budapest Setup
A51The Budapest strike: the trap-laden pawn sacrifice.
Old Benoni Setup
A43The Old Benoni: the immediate ...c5 counterstrike.
KIA Setup
A07The KIA setup: the universal system begins.
Plans & pawn structures
- 1In this open centre, development speed and king safety trump material — get castled, connect the rooks onto the open lines, and look for tactics against the less-coordinated side.
- 2Develop with a purpose: connect the pieces to a concrete plan (a break, a target square, an outpost) instead of making automatic moves.
- 3Watch the pawn breaks — both yours and your opponent's. In these structures the player who times the central break better usually wins the game.
Typical middlegame structures
The main line leads to an open centre — the central pawns have largely been traded, so open files and piece activity decide the game rather than pawn play. No files have opened yet, so this is a manoeuvring struggle: improve your pieces and prepare the pawn break that will open the position on your terms.
Traps & tactical motifs
Every sharp opening has its traps — study the forcing lines around the centre and the f7/f2 squares before playing this in rated games.
Watch the typical motifs: pins against the pinned piece, knight forks after the natural captures, and queen sorties to a2/g2-style squares.
How to Play Against the Flank Opening Deep Lines
- In this open position Black must match development tempo for tempo — fall behind on castling and coordination and the open lines turn against you at once.
Study plan & who it's for
Solidly intermediate. The main lines require real study, but the payoff is positions you can play for a lifetime. Best investment for White players around 1400–2000.
Play through the main line above until the piece setup feels natural.
Learn the two or three critical pawn breaks for both sides.
Drill one variation at a time — always connecting moves to plans.