Quick answer
Rule of the Square is an endgame technique: promotion race and tempo. Work from the first evidence position for Rule of the Square, and begin by testing d5.
Begin from d5 in 8/8/3p4/8/8/4P3/8/5K1k b - - 1 1. Count the material, king routes, promotion squares and reserve tempi before applying a theoretical rule. The evidence answer is: Rule of the Square: calculate both promotion paths and include checks before assuming the faster pawn wins. Candidate line: d5.
In the Rule of the Square example, notice: side Black; pieces Black pawn d6, White pawn e3, White king f1, Black king h1; legal first moves d5, Kh2. Read those squares as a snapshot of this single board, not as a standing rule you can copy into every game.
Material and result question
The first evidence board tests promotion race and tempo; the second board tests promotion race and tempo. Sequence A is direct FEN setup. Sequence B is direct FEN setup. Compare them only after setting both FENs. The Chess Wiki and the Endgames hub collect the shared vocabulary. Then compare Material Values with King And Pawn Versus King, Key Squares In Pawn Endgames, Corresponding Squares around the side-to-move tempo.
The two inventories make the distinction concrete. A contains side Black; pieces Black pawn d6, White pawn e3, White king f1, Black king h1; legal first moves d5, Kh2; B contains side Black; pieces Black pawn d6, White king d4, White pawn e3, Black king f3; legal first moves d5, Kg4, Kg3, Kg2, Kf2, Ke2. Compare the side to move before comparing the labels in the context of a reserve pawn move.
Topic dossier for this page and board pair r1:8 | r2:8 | r3:3p4 | r4:8 | r5:8 | r6:4P3 | r7:8 | r8:5K1k / r1:8 | r2:8 | r3:3p4 | r4:8 | r5:3K4 | r6:4Pk2 | r7:8 | r8:8: start with the side-to-move tempo; then test a reserve pawn move; keep the active rook before the pawn push separate from the conversion move order; use an outside passer used as a decoy as the transfer check; and reserve the defender's only active counterplay for the exception.
Conversion or defense plan
On the first board, calculate d5 after d5 and write down the opponent's best reply around the side-to-move tempo. On the second board, calculate Kf2 after Kf2 and check a reserve pawn move. Separate the practical conversion question from the result question; side to move and one checking distance can change the conclusion. In this case the useful condition is the defender's only active counterplay.
Key claim: Rule of the Square is illustrated here by promotion race and tempo; the first concrete test is d5. The board anchor is 8/8/3p4/8/8/4P3/8/5K1k; the example is intentionally narrower than the topic label and should not be generalised without checking the surrounding position..
Practical boundary: To answer “What exact king, pawn, and move-order conditions decide rule of the square, and how should each side play them?”, compare the recorded setup with Kf2 and the opponent's reply. The decision is useful only when the stated condition survives that concrete test on board 8/8/3p4/8/3K4/4Pk2/8/8. The evidence records No tablebase outcome is asserted by this generated record; verify the exact FEN before publication and the second board signature r1:8 | r2:8 | r3:3p4 | r4:8 | r5:3K4 | r6:4Pk2 | r7:8 | r8:8. The false-positive test is whether the active rook before the pawn push appears without the conversion move order, so the conclusion is useful only when the stated condition survives that concrete test.
Evidence positions
example-1: promotion race and tempo
Show answer
Rule of the Square: calculate both promotion paths and include checks before assuming the faster pawn wins. Candidate line: d5.
Why this position is here: Rule of the Square is represented by promotion race and tempo. This is a direct FEN setup with board anchor 8/8/3p4/8/8/4P3/8/5K1k; no opening history is inferred from the diagram.
FEN: 8/8/3p4/8/8/4P3/8/5K1k b - - 1 1
Question: What is the first concrete decision in this rule of the square position?
Answer cue: Rule of the Square: calculate both promotion paths and include checks before assuming the faster pawn wins. Candidate line: d5. The first candidate to test is d5. Replay d5 on board anchor 8/8/3p4/8/8/4P3/8/5K1k and write down what changes after it.
Evidence boundary: No tablebase outcome is asserted by this generated record; verify the exact FEN before publication.
example-2: promotion race and tempo
Show answer
Rule of the Square: calculate both promotion paths and include checks before assuming the faster pawn wins. Candidate line: Kf2.
Why this position is here: Rule of the Square is represented by promotion race and tempo. This is a direct FEN setup with board anchor 8/8/3p4/8/3K4/4Pk2/8/8; no opening history is inferred from the diagram.
FEN: 8/8/3p4/8/3K4/4Pk2/8/8 b - - 5 3
Question: What is the first concrete decision in this rule of the square position?
Answer cue: Rule of the Square: calculate both promotion paths and include checks before assuming the faster pawn wins. Candidate line: Kf2. The first candidate to test is Kf2. Replay Kf2 on board anchor 8/8/3p4/8/3K4/4Pk2/8/8 and write down what changes after it.
Evidence boundary: No tablebase outcome is asserted by this generated record; verify the exact FEN before publication.
example-3: promotion race and tempo
Show answer
Rule of the Square: calculate both promotion paths and include checks before assuming the faster pawn wins. Candidate line: e4 Kf2.
Why this position is here: Rule of the Square is represented by promotion race and tempo. This is a direct FEN setup with board anchor 8/8/3p4/8/8/4P3/3K2k1/8; no opening history is inferred from the diagram.
FEN: 8/8/3p4/8/8/4P3/3K2k1/8 w - - 2 2
Question: What is the first concrete decision in this rule of the square position?
Answer cue: Rule of the Square: calculate both promotion paths and include checks before assuming the faster pawn wins. Candidate line: e4 Kf2. The first candidate to test is e4. Replay e4 Kf2 on board anchor 8/8/3p4/8/8/4P3/3K2k1/8 and write down what changes after it.
Evidence boundary: No tablebase outcome is asserted by this generated record; verify the exact FEN before publication.
Reading the line
Read the first example (id example-1) as a complete record: continuation d5, source tablebase. This is a direct FEN setup with board anchor 8/8/3p4/8/8/4P3/8/5K1k; no opening history is inferred from the diagram. If A does not expose promotion race and tempo, correct the evidence before relying on the prose.
Read the second example (id example-2) separately: continuation Kf2, source tablebase. Its feature is promotion race and tempo; inventory side Black; pieces Black pawn d6, White king d4, White pawn e3, Black king f3; legal first moves d5, Kg4, Kg3, Kg2, Kf2, Ke2. Compare what changes between d5 and Kf2.
Boundary cases
The main mistake to avoid with Rule of the Square is applying a remembered endgame rule while ignoring side to move, king placement or an unverified result. In A, the missing condition must be located in r1:8 | r2:8 | r3:3p4 | r4:8 | r5:8 | r6:4P3 | r7:8 | r8:5K1k after d5; in B, test it against r1:8 | r2:8 | r3:3p4 | r4:8 | r5:3K4 | r6:4Pk2 | r7:8 | r8:8 after Kf2.
For Rule of the Square, the first board's evidence boundary (after d5) is No tablebase outcome is asserted by this generated record; verify the exact FEN before publication. The second board's evidence boundary for Rule of the Square is No tablebase outcome is asserted by this generated record; verify the exact FEN before publication. If a trusted source or careful calculation changes the conclusion around an outside passer used as a decoy, update both the evidence record and this article.
Practice from a real game
play the position for both sides, record the critical tempo, and verify the exact FEN against the cited tablebase before publication. Start with A's side to move and r1:8 | r2:8 | r3:3p4 | r4:8 | r5:8 | r6:4P3 | r7:8 | r8:5K1k; record two candidates, the reply to d5 and the correction. Repeat with B's side to move and r1:8 | r2:8 | r3:3p4 | r4:8 | r5:3K4 | r6:4Pk2 | r7:8 | r8:8; the changed board tests transfer rather than diagram memory.
After the drill, compare your notes with King And Pawn Versus King, Key Squares In Pawn Endgames, Corresponding Squares through the conversion move order. Keep A's rejected alternative beside B's chosen line Kf2; this shows whether the conclusion survived a new board signature.
Sources and scope
Sources for Rule of the Square: Syzygy tablebase verification reference, 1chess.online editorial scope. Source ids are tablebase, original-analysis. Primary evidence hook: tablebase. Comparisons and practice notes are editorial. Evidence revision: 2026-08-remediation-r2.
Scope note for board pair r1:8 | r2:8 | r3:3p4 | r4:8 | r5:8 | r6:4P3 | r7:8 | r8:5K1k / r1:8 | r2:8 | r3:3p4 | r4:8 | r5:3K4 | r6:4Pk2 | r7:8 | r8:8: this page does not claim that d5 is an engine principal variation, that an exact endgame result is verified when the evidence says it is not, or that a tool output replaces human calculation. The conclusion is limited to the recorded boundary and the exception the active rook before the pawn push.