It was around the year 1300 that a pawn was first allowed to advance two squares on its first move. This was supposed to be a unique privilege for the pawn. The En Passant rule came nearly two centuries later, to counter those who (mis)used this privilege as a way to sneak through a firing line. In many ways, this rule is consistent with the inherent justice of chess. Crossing a firing line is fraught with risk, but it is only fair that once you cross it, you are safe from that particular danger. Some European countries, mainly Italy, had a different set of chess rules until 1881. In fact, It was on this week exactly 140 years ago that the Italians became the last major chess nation at the time to adopt the modern rules, which included en passant, castling and pawn promotion. There is no better way to celebrate the 140th anniversary of it being universally accepted than exploring some en passant related curiosities. Bug in the system Even today, en passant remains a mysterious maneuver for most newcomers. In over-the-board tournaments for kids, arbiters get called upon regularly (“His pawn cheated, sir”) when someone makes an en passant capture. Major online chess platforms say that their support teams regularly get emails complaining about a ‘bug’ which sometimes allows a pawn to capture another pawn ‘illegally’. So it is not a surprise that this rule was the reason for the only recorded incident in history where both the players ‘allegedly’ resigned at the same time. The following position is said to have occurred in a game played in 1923 between two nameless players. [caption id="attachment_160573" align="alignnone" width="300"] Black played 1...g5+ here and …. resigned![/caption] Black is said to have noticed just a tad too late that white could checkmate him by capturing the pawn en passant with 2.hxg6 e.p. The story goes that white, having never heard of a thing as en passant, also accepted defeat precisely at the same moment, because he himself is checkmated if not for the possibility of en passant. The whole episode is probably apocryphal, but it certainly draws a chuckle. Some ‘impossible’ riddles Can you unpin an enemy piece and pin it at the same time? It sounds impossible. [caption id="attachment_160574" align="alignnone" width="300"] White to play[/caption] White wins a rook with 1.c4+, unpinning the black b-pawn and pinning it at the same time. Here’s another. Is it possible to give a discovered check by removing an enemy piece from the checking line? Surely you can remove an enemy piece only by capturing it, in which case it won’t be a discovered check. But it turns out, where there is an en passant, there is a way. [caption id="attachment_160578" align="alignnone" width="300"] White to play[/caption] 1.Nxe6+ g5 2.hxg6 e.p# It’s indeed a double discovered check with three key lines being cleared. Food for thought The French term ‘en passant’ (in passing) comes from the fact that the enemy pawn can capture the just-moved pawn "as it passes" through the first square. If you flatter yourself as someone who already got all this figured out, have a look at the following. [caption id="attachment_160579" align="alignnone" width="300"] White to play - From Adventure in Chess by Assiac (1951) [/caption] Here, white played 1.Bg2+ and announced a mate to follow. Black immediately refuted this claim and played 1...d5+ and announced a mate (discovered check by the bishop) himself. White argued that he can play 2.cxd6 e.p, and that the black pawn never reached the d5 square to interpose the earlier check. After all, the term en passant literally means the pawn was captured “as it passes” the d6 square, and the universally accepted way of recording it also suggests the pawn was captured on d6. So, did the black pawn ever reach the d5 square to save his king? Who is actually mated here? Is it neither, or both? Of course we know that according to the rules black has checkmated white with the 1...d5+ move, but somehow it just doesn't feel right.