6.h4 Main Line - King's Indian Defense
6.h4 Main Line
Definition
“6.h4 Main Line” is the name most often given to the variation of the King’s Indian Defence that arises after the moves 1.d4 Nf6 2.c4 g6 3.Nc3 Bg7 4.e4 d6 5.Nf3 O-O 6.h4. The label “Main Line” distinguishes the critical continuations after 6…e5, 6…c5 or 6…Bg4 from the numerous side systems in which Black avoids direct confrontation. Although the same pawn advance (h2–h4 on move six) can occur in other openings—most notably the Najdorf Sicilian—the term “6.h4 Main Line” without qualifiers is understood by theory manuals, databases and ECO codes (E90–E92) to refer to the King’s Indian system pioneered by Grandmaster Lubomir Kavalek and popularised by Alexei Shirov, Alexander Morozevich and the modern engine era.
Strategic Purpose
White’s sixth-move pawn thrust serves three interconnected strategic functions:
- Space and Clamp: By seizing h5 and possibly g6, White clamps down on Black’s customary kingside expansion …f7–f5 or …g6–g5.
- Direct Attack: The pawn may continue to h5 to open the h-file with h5×g6 or to soften g7, creating tactical motifs such as Bc1–h6 or Ng5.
- Flexibility: Because the move does not yet commit the g-pawn or light-squared bishop, White can later choose between classical setups (Be2, 0-0), fianchetto plans (Bg2) or aggressive queen-side expansion with Be3, Qd2 and 0-0-0.
Key Continuations
After 6.h4 the play usually branches into three principal continuations:
- 6…e5 7.d5 Na6 – The “Classical” path where Black attacks the centre while White storms the kingside. Theory regards 8.h5 or 8.Be2 as the main tries.
- 6…c5 7.d5 e6 – A Benoni-style structure in which Black hopes to undermine d5 before White’s flank attack becomes decisive.
- 6…Bg4 7.Be2 Nc6 – Black pins the knight to slow down h4-h5 ideas, but at the cost of revealing his own king.
Historical Notes
• The earliest specialist was GM Lubomir Kavalek in the late 1960s,
earning the ECO sub-code “Kavalek Variation”.
• The line went mainstream after the 1990s when Alexei Shirov and
Alexander Morozevich used it to score spectacular attacking wins against
elite opposition.
• Modern engines validate White’s space-gaining concept, refreshing the
line with novelties such as the pawn sacrifice 8.h5 Nxh5 9.Be2! seen in
correspondence and Titled-Tuesday games.
Illustrative Games
-
Shirov – Gelfand, Linares 1998
Shirov uncorked 6.h4 and later offered an exchange sacrifice to keep the h-file open, eventually mating the Black king on g7. -
Morozevich – Topalov, Wijk aan Zee 2001
A model attacking game showing the motif h4-h5, Bc1-h6 and queen lift Qd1–f3–h3. -
Caruana – Radjabov, Candidates 2020
Demonstrates a modern, engine-assisted “slow burn” version where h4 restrains Black’s kingside counterplay while the centre and queen-side are prepared.
Example Position
The following mini-PGN shows one of the most topical theoretical battles as of 2023:
Typical Plans
- For White
- Push h4-h5 at the earliest safe moment.
- Place a knight on g5 to exploit the weakened f7 and h7 squares.
- Exchange dark-squared bishops with Bh6 when Black plays …e7–e5.
- Keep central tension (d4–d5 pawn wedge) until the kingside break becomes decisive.
- For Black
- Counter in the centre with …e5 and …c6 or …c5 to divert the attacking pieces.
- Consider the manoeuvre …Na6–c5 to hit e4 and d3 squares.
- If permitted, launch …f7–f5 to generate counter-play on the kingside before White’s pawn reaches h5.
- Swap minor pieces (…Bg4, …Bxf3) to reduce attacking material.
Interesting Facts
- The move 6.h4 violates the classical dictum “Do not move a wing pawn before the centre is settled.” Ironically, its success is based on modern principles of space, initiative and concrete calculation.
- Engines often evaluate the starting position after 6.h4 as +0.30 to +0.50 for White, a surprisingly large plus against a main-line defence that has been analysed for 70+ years.
- Some Najdorf specialists (e.g., Magnus Carlsen) borrowed the same idea in the Sicilian: 1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 a6 6.h4!? creating psychological surprise value.