Avalanche Chess

Invented by Ralph Betza, 1977. One of the most popular postal Chess variants, described in Pritchard’s Encyclopedia of Chess Variants and Popular Chess Variants, and in Schmittberger’s New Rules for Classic Games.

Overview

Avalanche Chess adds a compulsory obligation to every move: after making a normal chess move, you must push one of your opponent’s pawns one square toward you. This “pawn push” creates an avalanche of pressure as the opponent’s pawns steadily advance.

Setup

Standard FIDE starting position.

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Rules

All standard FIDE rules apply, with the following modifications:

The Two-Part Turn

Each turn consists of two parts, both of which must be completed:

1. Move: Make any legal chess move (normal move, capture, castling, etc.).
2. Push: Advance one of the opponent’s pawns one square forward (toward yourself). The push is a single square only and is never a capture.

Constraints on the Push

• The push is obligatory unless the opponent has no pawn that can legally be advanced (all pawns blocked).
• The pawn being pushed must have a clear square immediately in front of it (no piece in the way).
• A player’s first part of the turn (the move) must be legal according to standard rules. A player cannot leave their King in check after part 1, planning to escape check in part 2 — the two parts do not interact: check must be resolved in part 1.

Losing by Push

• If pushing an opponent’s pawn causes the pushing player’s own King to be in check (i.e., the moved pawn reveals or creates a check against the pusher), that player loses immediately, even if they checked or mated the opponent in part 1 of the same turn.

Promotion by Push

• If a pushed pawn reaches the last rank (promotion rank), the pawn’s owner chooses what piece it promotes to.
• If the promotion results in a check against the player who did the pushing, that player loses immediately.

No En Passant

En passant captures are not used in Avalanche Chess.

Balanced Avalanche Chess

White has a substantial first-move advantage in standard Avalanche Chess. To compensate, Balanced Avalanche Chess (Alessandro Castelli) removes White’s pawn push on the very first move: White’s first turn consists of the move only; from White’s second turn onward, both parts are required.

Strategy Notes

The pawn push dramatically changes strategy. A player must think not only about their own position but also which of their pawns are most dangerous when advanced. Passed pawns become double-edged: your opponent can race them to promotion. Check threats must be calculated with great care since a push that exposes your own King loses the game instantly.

Source: chessvariants.com/mvopponent.dir/avalanche.html