Training notebook · Endgames
Rule of the square: count a pawn race correctly
The rule of the square helps judge whether a king can catch a lone pawn. Learn its assumptions before applying it to a crowded pawn race.
What the square measures
For an unobstructed pawn running toward promotion, compare the remaining pawn advances with the defending king's available steps. The familiar imaginary square is a visual shortcut for that race. It helps you avoid calculating every move when the relevant squares are empty and neither king can interfere.
The side to move matters. Count from the actual position, and account for an available initial two-square pawn move. A pawn still on its starting rank can cover two ranks in one move if the path is clear. Treating it like a pawn that can advance only one square gives the defender an extra tempo that does not exist.
When the shortcut is not enough
Other pieces, a supporting king and blocked routes can invalidate a simple race count. A king may seem close enough but be forbidden from crossing a controlled square. A pawn may appear unstoppable but need a preparatory move to escape a blockade. Checks elsewhere can also change the timing.
Promotion is not always the end of the calculation. Check whether the newly promoted piece can be captured immediately and whether promoting creates a tactical problem for the king. The square rule answers a narrow catching question; it does not certify that an entire ending is won.
Train counting before drawing
Use a physical board or an external legal study board with one pawn and a defending king. Predict the catch by counting moves first, then visualise the square and compare the answers. Play both sides to verify the route. Repeat with the other side to move and with the pawn one rank farther forward.
For the next round, add a supporting king or a blocked route and state explicitly why the original shortcut needs more calculation. Keep these examples separate from the clean ones. The goal is to recognise the rule's conditions rather than apply a diagonal shape to every position containing a pawn.
A useful error log
Record errors under three headings: tempo, route and promotion. Tempo means you counted the wrong player first or missed a double advance. Route means you allowed the king through an attacked square. Promotion means you stopped calculating before the new piece's safety was settled.
Retest one example from each category later without moving the pieces. Explain how the defending king reaches the pawn and where it would fail if placed one square farther away. A correct reason transfers to a new board; a remembered yes-or-no answer usually does not.
Try making the prediction with your eyes away from the board, then return to verify each step. This separates visual familiarity from counting skill. If the two methods disagree, locate the first mismatched move instead of repeatedly drawing the square until the preferred answer appears.
Put the practice into a routine
Where Brass Pawn fits
Use this as preparation for Brass Pawn's pawn-ending exercises. There is no claim that a standalone rule-of-the-square editor or drill is included; external study setup supplies the controlled comparisons.