Overprotection · For club players · 18 min read

Overprotection in Chess: Fischer's e5 Pawn v Myagmarsuren, 1967

Sousse 1967: Fischer guards one pawn on e5 three times, then sends its guards to the king. Stockfish 19 says the game was level until move 22, and names the one move that lost it.

FischerGM1–0MyagmarsurenInterzonal tournament, game 3 · Sousse · 1967 · French Defence, King's Indian Attack (C00)

Published 14 November 2026Checked by Stockfish 19 WASM Multithreaded, depth 21 to 31

The strong point holds up the attack+2.97White winning

After 23.Bf6 the pawn on e5, guarded since move 9, props the bishop on f6. Black cannot take it without opening the e-file and the g-file, and Qg5 with mate on g7 is coming. The strong point has become the attack's foundation.

threat
key square
outpost
target
Black's king zone
pawn chain or line of force

Analyse this position Play it out against Stockfish

In short

Overprotection means guarding a key pawn or square more times than it is attacked, so the opponent gives up attacking it and the guarding pieces are free to act.
At the Sousse Interzonal in 1967 Bobby Fischer guarded the pawn on e5 with a knight, a rook and a bishop. Black never challenged it with ...f6, turned to the queenside, and by move 19 the e5 pawn needed only one guard.
The pieces that had guarded e5 went to the kingside, and the pawn itself became the prop for a bishop on f6 next to Black's king.
Stockfish 19 shows the game was close to level until move 22: 22...Nc3 took the last central knight away from the kingside, while 22...c4 kept Black in the game. Fischer also missed two stronger moves on the way, 16.Ng5 and 22.Bg2.
To use it: find the one pawn your plan stands on, guard it until the opponent stops attacking it, then let the guards go to work.

How we know what we say

Verified From the record: Stockfish's numbers, the players' own notes or interviews, or a cited source.
Inferred Read from the moves and the position: a reasoned reconstruction, not the player's words.
Speculative A guess about mood, intent or practical motives: plausible, not proven.

Part 1The setting: Sousse 1967, Fischer against Mongolia's champion

The Interzonal tournament at Sousse, Tunisia, in the autumn of 1967 was the qualifying stage for the next world championship cycle. Bobby Fischer, then 24, was the favourite. The game against Lhamsuren Myagmarsuren of Mongolia came in round 3, on 15 October.

Myagmarsuren had qualified by winning the West Asian Zonal tournament in 1966, was a four-time Mongolian champion, and received the International Master title from FIDE in 1967. Myagmarsuren died on 26 October 2026, aged 88, and the ChessBase obituary singles out this loss to Fischer as a brilliant game that is still frequently cited. ^[3] Verified

The game never counted in the final table. Fischer won seven games and drew three, then withdrew from the tournament after a dispute over the playing schedule; Bent Larsen won the Interzonal with 15½ out of 21. The game survived anyway: Karsten Müller chose it as game 29 of Bobby Fischer: 60 Best Games. ^[6][5][4] Verified

The game at a glance.
	White	Black
Player	Robert James Fischer (United States)	Lhamsuren Myagmarsuren (Mongolia)
Later	World champion 1972, peak rating 2785	Four-time Mongolian champion
Opening	King's Indian Attack against the French	French structure, queenside pawn storm
Result	1-0 in 31 moves

Part 2What is overprotection in chess?

Overprotection means giving a strategically important pawn or square more protection than it seems to need. The idea comes from Aron Nimzowitsch's book My System: a well-guarded strong point discourages the opponent from attacking it, and the pieces that guard it stand on good squares from which they can later spring into action.

Jeremy Silman's definition adds the purpose: overprotection is essentially prophylactic, a way of talking the opponent out of attacking the point at all. ^[7] Verified

The point you overprotect must matter. A pawn on e5 that cramps the enemy king's side, a knight outpost, the base of a pawn chain: these are worth three guards. A pawn on a3 that nobody wants is not. And the guards must be useful pieces in their own right, not prisoners of their duty.

Worth it: the e5 strong point+0.05about equal

Four White units guard e5 (the d4 pawn, the bishop, the knight and the queen with the rook behind it) against two attackers (the queen and the knight). Black has no way to win the pawn, and every guard also looks at the kingside.

key square
Guards of e5
pawn chain or line of force

Analyse this position Play it out against Stockfish

Not worth it: guarding a pawn nobody wants0.00about equal

White's rook, bishop and knight all guard the a3 pawn, which Black is not attacking. Meanwhile Black's doubled rooks own the open d-file and threaten Rd1 mate, so White must spend the next move on the back rank. Guarding an unimportant point is just passivity.

threat
weakness
target
Black's open file

Analyse this position Play it out against Stockfish

The same idea, a good case and a bad one. On the left the overprotected pawn is the backbone of White's position; on the right three pieces guard a pawn that does not matter while the real fight is elsewhere.

Part 3How the King's Indian Attack builds the e5 wedge

Fischer met the French Defence with the King's Indian Attack: d3, Nd2, g3, Bg2 and castling, the King's Indian Defence with an extra move. Black answered with the most active set-up, ...d5, ...c5, ...Nc6 and castling short. On move 8 Fischer pushed e4-e5, driving the knight from f6 to d7.

1.e4 e6 2.d3 d5 3.Nd2 Nf6 4.g3 c5 5.Bg2 Nc6 6.Ngf3 Be7 7.O-O O-O 8.e5 Nd7 9.Re1 −0.16about equal

The King's Indian Attack against the French: by move 9 the pawn on e5 is guarded by the knight on f3 and the rook on e1.

The pawn on e5 is the whole point of White's set-up. It takes the f6 square from Black's knight, the best defender of a castled king, and it gives White room on the kingside. Black's natural answer in French structures is to strike at it with ...f7-f6 or to pile up on it with ...Qc7. Black did neither: the next eight moves went into a pawn storm on the queenside. Inferred

The wedge on e5 and the race−0.16about equal

After 9.Re1 the e5 pawn is guarded twice and attacked twice (the knights on d7 and c6). Black's pawns on c5, d5 and e6 form a chain pointing at the queenside, where the pawn storm will come; White's space is on the kingside.

key square
White's kingside space
Black's queenside storm
pawn chain or line of force

Analyse this position Play it out against Stockfish

This structure is the King's Indian Attack's mirror of the Advance French, where White also builds on a pawn on e5 and Nimzowitsch first taught the idea of guarding the chain's key points more than strictly needed.

Part 4Two plans: a kingside attack against a queenside storm

By move 14 the plans were set. White reroutes the queen's knight by f1 to e3, pushes the h-pawn to h4 and h5, and aims the queen, the knight and the light-squared bishop at h7. Black storms with the a- and b-pawns, opens the b-file and brings the knights to a5 and the queenside squares c4 and b3.

White: the guards look at the king+0.63White slightly better

Every piece guarding e5 can turn to the kingside: the knight on f3 can jump to g5, the bishop on f4 can go to g5 and f6, and the queen reaches h5. The pawn on e5 keeps Black's knight off f6.

plan
key square
target

Analyse this position Play it out against Stockfish

Black: files and squares on the queenside+0.63White slightly better

Black has opened the b-file and put a knight on a5, heading for c4 or b3. The c-pawn can advance to c4 to open more lines. Not one Black piece is aimed at the e5 pawn any longer.

plan
outpost
target

Analyse this position Play it out against Stockfish

The same position after 14...Na5, seen by both sides. White's attack needs the e5 pawn to hold without help; Black's counterplay needs time on the other wing.

Here is where overprotection pays its first dividend. Because the pawn on e5 is guarded three times (knight, bishop, rook) and attacked only by the knight on d7, Black gives up on it. When 14...Na5 sends the second knight to the edge, e5 is attacked once and guarded three times, and White's guards are free to look elsewhere. Inferred

Stockfish rates 14...Na5 as a small concession, preferring 14...Rb8 with the knight still on c6, where it watches e5 and the central squares. After 14...Na5 the engine's edge for White rises to about two-thirds of a pawn. Verified

Part 5The critical moments: where the strong point decided the game

Stockfish 19 across the game, from White's side. The line hugs zero until move 21, rises at 21...Rfc8 and 22...Nc3, and breaks after 24...g6. Above the line White is better, below it Black; the diamonds are the critical moments.

1 12.Bf4 Add a third guard to e5, or race on the kingside?
2 16.Bh3 Attack h7 at once, or shut down the ...f6 break?
3 21...Rfc8 Where should Black's last reserves go?
4 22.Nd2 Hit the defender, or bring another attacker?
5 22...Nc3 Keep the knight on d5, or send it into White's camp?

Critical moment 1 of 5 · Move 12, White to play

Add a third guard to e5, or race on the kingside?

threat
key square

Your move as Fischer

White to play. Black's a- and b-pawns are rolling, and the e5 pawn is guarded by the knight and rook and attacked by both Black knights. How should White treat the pawn?

Think it through on the board

Weigh the candidates

Move	Stockfish	Verdict
12.N1h2 12...Ba6 13.Ng4	0.00about equal	Stockfish's narrow first choice: the knight heads for g4, close to level. Verified
12.h5 12...h6	−0.28about equal	Gains space but leaves e5 guarded only twice; about level. Verified
12.c4	0.00about equal	Also level for Stockfish: White strikes at the queenside instead of the centre. Verified

What Fischer played

12.Bf40.00about equal

Fischer played 12.Bf4, adding a third guard to e5. Now the pawn is attacked twice and guarded three times, and the bishop also looks along c1-h6 toward the kingside.

Stockfish's first choice too. Depth 26.

What it revealed

The choice shows Fischer's priority: before the race, make the one pawn the attack depends on secure. A secure e5 means Black's natural break ...f6 only opens lines for White's pieces.

What Stockfish adds Stockfish sees the position as balanced: the strong point is not yet an advantage, only a promise.

Verified Stockfish rates 12.Bf4 and 12.N1h2 almost equally, both close to level: the overprotection costs nothing.
Inferred After 12.Bf4 Black never again attacks e5 with a second piece. The next Black moves go to the queenside (...a4, ...bxa3, ...Na5).

Within three moves the c6-knight went to a5 and e5 had one attacker left: Black had been talked out of the fight for e5. Inferred

Critical moment 2 of 5 · Move 16, White to play

Attack h7 at once, or shut down the ...f6 break?

idea not played
target

Your move as Fischer

White to play after 15...Ba6. The knight on f3 is no longer needed on e5, and Black's king has only the knight on d7 nearby. What is White's most forceful continuation?

Think it through on the board

Weigh the candidates

Move	Stockfish	Verdict
16.Ng5 16...Nc6 17.Qh5 Bxg5 18.hxg5	+1.49White clearly better	Stockfish's choice: Qh5 and mate on h7 is threatened, about a pawn and a half for White. Verified
16.Rb1	+0.87White slightly better	Takes the open b-file first; Stockfish's second choice, nearly a pawn better for White. Verified
16.Ng4	+0.54White slightly better	Aims at f6 and h6, about half a pawn for White. Verified

What Fischer played

16.Bh3+0.13about equal

Fischer played 16.Bh3, aiming the bishop at e6. Now ...f7-f6 would leave e6 hanging with check, so Black's only break against e5 is gone for good.

Stockfish preferred 16.Ng5 (+1.54); the game move gave up about 1.4 pawns. Depth 24.

What it revealed

Fischer chose a prophylactic move over the most forcing one: kill the opponent's last chance to attack the strong point, then attack. Stockfish prefers the direct 16.Ng5, but the bishop on h3 later supports the whole kingside attack.

What Stockfish adds Stockfish's 16.Ng5 threatens Qh5 and Qxh7 mate at once; after 16...Nc6 17.Qh5 Bxg5 18.hxg5 White keeps an edge of more than a pawn.

Verified Stockfish values 16.Ng5 at about a pawn and a half for White and 16.Bh3 at close to level: the whole edge was let go.
Verified The ...f6 break is the test. With the bishop on h3, Stockfish answers 18...f6 with 19.Bxe6+ and White is winning; earlier, after 9.Re1, the same break cost Black less than half a pawn.
Speculative Fischer may have preferred the slower move because it removed all of Black's counterplay against the centre, a choice that fits a style built on denying the opponent chances.

Critical moment 3 of 5 · Move 21, Black to play

Where should Black's last reserves go?

threat
outpost
key square
target

Your move as Myagmarsuren

Black to play after 21.Qh5. White's queen and the bishop on g5 stare at the kingside. Black's knight on d5 is the only piece near the king. What does the position ask of Black?

Think it through on the board

Weigh the candidates

Move	Stockfish	Verdict
21...Bb7 22.Nh2 Qe8	+0.27about equal	Stockfish's choice: the bishop guards d5 and the long diagonal; close to level. Verified
21...Nc6	+0.69White slightly better	Brings the knight back toward the centre; White about two-thirds of a pawn better. Verified
21...Qe8	+0.68White slightly better	Guards f7 and g6 at once; White about two-thirds of a pawn better. Verified

What Myagmarsuren played

21...Rfc8+2.31White winning

Myagmarsuren played 21...Rfc8, moving the king's rook to the c-file to support ...c4 and the queenside play.

Stockfish preferred 21...Bb7 (+0.29); the game move gave up about 2.0 pawns. Depth 23.

What it revealed

Black was still playing the queenside race, but with the rook gone from f8 the king lost a defender, and the knight on d5 was now the one piece holding the kingside together.

What Stockfish adds Stockfish's best reply to 21...Rfc8 is 22.Bg2, hitting the knight on d5 with the bishop and freeing h3; the engine rates White about two pawns better.

Verified Stockfish rates 21...Rfc8 as an error that hands White about two pawns if White finds the reply.
Inferred 21...Bb7 was the way to defend: it adds a guard to the d5 knight, the piece that covers f6 and e3, so White cannot simply chase it away.

Critical moment 4 of 5 · Move 22, White to play

Hit the defender, or bring another attacker?

plan
target
key square

Your move as Fischer

White to play after 21...Rfc8. The knight on d5 is Black's only central defender. Which White move makes the most of Black's last rook move?

Think it through on the board

Weigh the candidates

Move	Stockfish	Verdict
22.Bg2 22...Nc6 23.Be4 h6 24.Bxh6	+2.23White winning	Stockfish's choice: the bishop hits d5 and heads for e4 and h7, about two pawns for White. Verified
22.Nh2 22...Qe8 23.Bf6	+2.22White winning	Almost as strong: the knight heads for g4 to support Bf6; about two pawns for White as well. Verified

What Fischer played

22.Nd2+0.26about equal

Fischer played 22.Nd2, bringing the last knight toward e4 and f6. The knight joins the attack and the bishop stays on h3, aimed at e6.

Stockfish preferred 22.Bg2 (+2.31); the game move gave up about 2.0 pawns. Depth 23.

What it revealed

Fischer added an attacker rather than removing a defender. Stockfish shows the difference: the knight on d5 is what holds Black's position, and 22.Bg2 attacks it at once (22.Nh2, heading for g4, is nearly as strong).

What Stockfish adds After 22.Nd2 Stockfish's defence is 22...c4, keeping the knight on d5 and opening the c-file at once; the engine then sees the game close to level.

Verified Stockfish rates 22.Nd2 as letting most of the edge go: after it White is less than half a pawn better.
Inferred The miss is a reminder that strong attackers err too. Fischer's attack was right in its plan and imprecise in its moves; the opponent had to find the defence.

Part 6The turning point: 22...Nc3 and the empty f6 square

Critical moment 5 of 5 · Move 22, Black to play

Keep the knight on d5, or send it into White's camp?

threat
outpost
key square
weakness

Your move as Myagmarsuren

Black to play after 22.Nd2. White's knight is coming to e4, and the bishop on g5 looks at f6. Black's knight on d5 could jump forward into White's position. What should Black do?

Think it through on the board

Weigh the candidates

Move	Stockfish	Verdict
22...c4 23.Bf6 Qe8 24.dxc4 Bxc4	+0.25about equal	Stockfish's choice: the c-file opens at once and the knight stays on d5; close to level. Verified
22...Nc6	+1.53White clearly better	Covers e5 and e7, but slow; White about a pawn and a half better. Verified
22...Qe8	+1.99White clearly better	Defends passively; White about two pawns better. Verified

What Myagmarsuren played

22...Nc3+3.05White winning

Myagmarsuren played 22...Nc3, a knight in White's camp eyeing e2, d1 and b1. It looks active, but now only the g7 pawn covers f6.

Stockfish preferred 22...c4 (+0.26); the game move gave up about 2.8 pawns. Depth 21.

What it revealed

Black still trusted the queenside race. The knight was the last piece between White's attackers and the f6 square; once it left, the e5 pawn could prop a bishop on f6 next to the king.

What Stockfish adds Stockfish rates 22...Nc3 a serious mistake: 22...c4 kept the position close to level, while after 22...Nc3 White is about three pawns ahead in the engine's eyes.

Verified Stockfish's evaluation jumps from close to level to about three pawns for White: the largest single swing of the middlegame.
Inferred On the board the threat is plain after 23.Bf6: if Black passes, Qg5 and Qxg7 is mate, and the bishop on f6 is guarded by the e5 pawn.
Inferred The knight on c3 also invites White's knight to e4. When Black exchanges there, White's rook recaptures on e4 and swings along the fourth rank to h4, which is how the game was won.

After 23.Bf6 Qe8 24.Ne4 Black played 24...g6, closing the g-file but fixing the dark squares around the king. Stockfish prefers 24...Bb7, close to three pawns worse for Black but with chances to resist; after 24...g6 the engine has White about five pawns ahead. After 24...g6 the finish is forced in spirit: Qg5 and Qh6 aim at g7, the rook arrives on h4, and h5 breaks open the h-file. Verified

Mate on g7 or on h8#3White mates by force

After 30...Qf8 the queen on h6, the rook on h4, the h5 pawn and the bishop on f6 surround Black's king. 31.Qxh7+ Kxh7 32.hxg6+ Kg8 33.Rh8 is mate. The e5 pawn still props the bishop on f6.

the move
plan
target
key square
outpost
The mating net

Analyse this position Play it out against Stockfish

25.Qg5 Nxe4 26.Rxe4 c4 27.h5 cxd3 28.Rh4 Ra7 29.Bg2 dxc2 30.Qh6 Qf8 31.Qxh7+ Kxh7 32.hxg6+ Kg8 33.Rh8# 1–0White completely winning

The finish: the rook comes to e4 by the exchange on e4 and swings to h4. Black resigned after 31.Qxh7+, before 31...Kxh7 32.hxg6+ Kg8 33.Rh8 mate. Verified

Part 7What Myagmarsuren could have done

Black's position was not bad. Stockfish shows the game near level until move 21, and twice afterwards Black had a defence that kept it close: 21...Bb7 instead of 21...Rfc8, and 22...c4 instead of 22...Nc3. Verified

The defence: open the c-file, keep the knight+0.25about equal

22...c4 hits d3 at once, so White has to spend time on the queenside, and the knight stays on d5, where it covers f6, e3 and f4. Black's counterplay arrives before White's attack is ready.

threat
plan
outpost
target
key square

Analyse this position Play it out against Stockfish

22...c4 23.Bf6 Qe8 24.dxc4 Bxc4 25.Ne4 Qf8 26.Qg4 Kh8 27.Bg5 Nc6 28.Bf4 +0.14about equal

Stockfish's defence after 22.Nd2: the queen guards g7 from f8, the bishop reaches c4, and White's attack has no clear breakthrough. Verified

Note one trap in this line: after 22...c4 23.Bf6, taking the bishop with 23...Nxf6 loses, because 24.exf6 opens the e-file onto e6 and the bishop on h3 takes there. The defender's knight must stay on d5 as a guard, not as a capturer: Stockfish rates 23...Nxf6 as losing outright. Verified

Part 8A different angle: the guards left, the pawn stayed

The game is usually told as a mating attack: Qh5, Bf6, Rh4, Qxh7+. Stockfish tells a different story. Through move 21 Stockfish keeps the evaluation within about a pawn, and mostly much closer; the one big chance was 16.Ng5 after 15...Ba6, which Fischer passed up. The attack did not crash through a weak position; it was let in by two Black moves in a row. Verified

That is the part of Nimzowitsch's idea the usual accounts skip. The value of guarding a point many times is that the opponent stops attacking it; when the attack on it stops, the guards are free and the point still stands. Black never played ...f6 and moved both knights away from e5, so the pawn needed only the rook. Inferred

Stockfish's turning points (White's view, in words).
Move	Played	Stockfish preferred	What changed
14...Na5	Knight to the rim, e5 attacked once	14...Rb8	Small edge to White
16.Bh3	Stops ...f6 for good	16.Ng5	An edge of about a pawn and a half let go
21...Rfc8	Rook leaves the king	21...Bb7	About two pawns if White finds 22.Bg2
22.Nd2	Another attacker	22.Bg2	Back to close to level
22...Nc3	The last defender leaves	22...c4	About three pawns for White
24...g6	Dark squares fixed	24...Bb7	Winning for White

The same rule ties this game to other strategies on the site. Guarding e5 so well that ...f6 stops working is prophylaxis: stopping the opponent's plan before your own. And Black's queenside storm against a pawn chain is the subject of attacking the base of a pawn chain.

Part 9How to use overprotection in your games

The recipe

Name the strong pointFind the one pawn or square your plan depends on: an advanced pawn like e5, an outpost, the base of your chain. If it fell, would your plan fall? Then it is worth overprotecting.
Count attackers and guardsList every enemy piece and pawn that can attack it, including breaks like ...f6. Guard it one more time than it can be attacked, with pieces that stand well anyway.
Kill the pawn breakA pawn attacking your strong point is worse than a piece, because you cannot chase it away. Make the break cost something, as 16.Bh3 did by aiming at e6.
Watch the opponent give upWhen the attackers leave (a knight to the rim, a queen to the other wing), your guards are free. Move them to the attack one at a time, keeping at least one guard.
Use the point as a propThe strong point now supports your pieces: a pawn on e5 holds a bishop or knight on f6 or d6 next to the enemy king.

Is this the pawn my plan stands on?
How many times can it be attacked, and by which pawn break?
Are my guards on squares that also help the attack?
Has the opponent stopped attacking it? Then which guard can leave first?
Which enemy piece guards the squares next to my strong point, and can I chase it away?

Your turnPractise it

Set each position up, decide your plan before you look, then play it out against Stockfish to see whether it holds.

White to play after 15...Ba6. Find the most forceful move against Black's king.

Hint

The knight on f3 is no longer needed on e5. Which square brings it next to h7, with the queen to follow?

A good answer

16.Ng5, threatening 17.Qh5 and Qxh7 mate. Stockfish rates White about a pawn and a half better; Fischer's 16.Bh3 was close to level.

Play it out Analyse

White to play after 21...Rfc8. Which move makes the most of Black's rook leaving f8?

Hint

Black's kingside rests on one piece. Attack it.

A good answer

22.Bg2, attacking the knight on d5 and heading for e4 and h7. Stockfish rates White about two pawns better. The game's 22.Nd2 let most of it go.

Play it out Analyse

Black to play after 22.Nd2. Find the move that keeps the game close to level.

Hint

The knight on d5 should stay. Use a pawn to open a file and hit d3.

A good answer

22...c4, opening the c-file at once while the knight stays on d5 to cover f6. Stockfish sees it close to level; 22...Nc3 gave White about two pawns.

Play it out Analyse

Black to play after 24.Ne4. The bishop on f6 already stands next to the king. Find Stockfish's most resilient defence.

Hint

A pawn move near the king fixes the dark squares for good. Look for a piece move that adds a defender to the long diagonal.

A good answer

24...Bb7, bringing the bishop to the long diagonal to challenge e4 and d5. White is still clearly better, but after 24...g6 White's queen reaches g5 and h6 and Stockfish rates White about five pawns better.

Play it out Analyse

Part 10Takeaways

Overprotect the point your plan stands on, not every pawn you have.
The aim is to make the opponent stop attacking it; then the guards are free.
Kill the pawn break first: 16.Bh3 made ...f6 impossible.
A strong point becomes a prop: e5 held the bishop on f6 next to the king.
The defender's last guard matters most: 22...Nc3 took the knight away from f6 and lost.
Great attackers miss moves too: Stockfish prefers 16.Ng5 and 22.Bg2 to Fischer's choices.

Questions readers ask

What is overprotection in chess?

Overprotection is guarding a strategically important pawn or square more times than it is attacked. The idea, from Aron Nimzowitsch's My System, is that a well-guarded strong point discourages the opponent from attacking it, and the guarding pieces stand on good squares from which they can later join an attack.

Who invented overprotection in chess?

Aron Nimzowitsch introduced overprotection in the 1920s in My System, alongside the blockade and prophylaxis. Players from Petrosian to Fischer used it, especially to support advanced central pawns such as a pawn on e5.

How did Fischer beat Myagmarsuren in 1967?

Fischer played the King's Indian Attack, pushed e4-e5 and guarded the pawn with a knight, a rook and a bishop. Black turned to a queenside pawn storm, the guards moved to the kingside, and after 22...Nc3 the e5 pawn propped a bishop on f6. Fischer mated with Qh6, Rh4 and Qxh7+ on move 31.

What is the difference between overprotection and prophylaxis?

Overprotection is one kind of prophylaxis. Prophylaxis means stopping the opponent's plan before it starts; overprotection does that for one specific point, by guarding it so heavily that attacking it is pointless. Fischer's 16.Bh3, which stopped the ...f6 break, was both.

Is overprotection good for beginners?

Yes, in a simple form: when one pawn holds your position together, add a guard before you start an attack. The harder part, for club players, is choosing which point matters and knowing when the guards can safely leave.

Sources and method

The game score was checked against two independent sources. Every position, line and candidate in this article was replayed for legality, and every engine number was produced by Stockfish 19 WASM Multithreaded for this article (depth 21 to 31, deepest at the critical moments), not copied from elsewhere. What the players thought is reconstructed from the moves, their published notes and later analysis; it is labelled as verified, inferred or speculative, and nothing is presented as a quotation unless a source is cited for it.

Part 1The setting: Sousse 1967, Fischer against Mongolia's champion

Part 2What is overprotection in chess?

Part 3How the King's Indian Attack builds the e5 wedge

Part 4Two plans: a kingside attack against a queenside storm

Part 5The critical moments: where the strong point decided the game

Add a third guard to e5, or race on the kingside?

What it revealed

Attack h7 at once, or shut down the ...f6 break?

What it revealed

Where should Black's last reserves go?

What it revealed

Hit the defender, or bring another attacker?

What it revealed

Part 6The turning point: 22...Nc3 and the empty f6 square

Keep the knight on d5, or send it into White's camp?

What it revealed

Part 7What Myagmarsuren could have done

Part 8A different angle: the guards left, the pawn stayed

Part 9How to use overprotection in your games

Your turnPractise it

Part 10Takeaways

Questions readers ask

Sources and method

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