As I said, these changes came in hundreds of years* ago. Around the same time, the Queen and bishop were powered up enormously. Given that en passant is rare anyway, I doubt there is any written evidence…
*the Gutenberg printing press was only invented about 50 years earlier, so I would be surprised to hear there was a chess magazine by that time!
It’s also worth noting that until comparatively recently, en passant wasn’t universal, and the Italian rule passar battaglia (which is Italian for “That’s just tough”*) applied in that country until the 1880s - long after the double move was invented.
*Not really
There’s more involved with a two-step past an adjacent pawn than just avoiding capture. Pawn play in chess revolves around trying to create a “passed pawn”–that is, a pawn not blocked by an enemy pawn on either its own or an adjacent file. Such a pawn becomes a queening threat, and can often tie down an enemy piece.
It becomes too easy to create a passed pawn if you can just two-step past an enemy pawn once the enemy reaches the fifth rank.
That’ll be news to Hans Kmoch, who wrote the epic Pawn Power in Chess, where he discusses concepts like pawn chains, the quartgrip, pawn structures favouring bishops, pawn structures favouring knights, melanopenia and leucopenia.
Bearing in mind that the pawn doing the two-step has never moved before, how likely is it that it will become a passed pawn? 
Have you got any Grandmaster games showing this happening?
Yes, yes, yes . . . so I should have said “one important aspect” of pawn play. So shoot me.
How could it happen, when the en passant rule allows the opponent to capture?
What do you think is the purpose of the rule, if not to prevent pawns from sliding past enemy pawns on the adjacent fifth rank?
I don’t mean to offend, but you claimed pawn play ‘revolves around creating passed pawns’. This is only a minor part of pawn play and (for example) pawn structure is far more important.
The purpose of the rule (as was said early in the thread) is indeed to prevent pawns sliding by.
But this has nothing to do with passed pawns.
(And I cannot recall a Grandmaster game where a player would have been able to create a passed pawn if the en passant capture did not exist.)
Sounds like you know better than me. I’m very far from an expert in chess strategy. I thought (incorrectly, I guess) that you weren’t following Boozahol Squid, P.I.'s claim that en passant captures can give pawns the opportunity to move towards the central files. Whether this is typically desirable or not is beyond me. I would think that making it harder to, say, move the pawn from the g file to the f file reduces that pawns value, but what do I know?
Or were you really just objecting to the fact that he (and I in expanding on it) used the term “center” when I think he really meant “middle two files”?
I don’t know. You know that one of the first books printed in English was 1474’s “Game and Playe of The Chesse”, right?
And, btw, the book talks about double moves for pawns.
Or, in more modern english,
And on capturing:
Or, my translation:
Can I submit this thread to the “Why is the SDMB Special” list?
I’m sorry if I get a bit carried away when chess is mentioned on the SDMB :o, but I am a professional chess teacher and internationally ranked player.
Given our motto demands precision, I do challenge imprecise chess statements.
It’s true that en passant can move a pawn closer to the centre files, but it can equally move it away.
I estimate that I use en passant about once every 500 games, so it’s really not an important part of pawn play.
Also given the capturing pawn ends up close to the enemy starting area, it’s usually recaptured immediately.
So I don’t think en passant adds much to a pawn’s value.
Your research is most impressive! 
However there is no discussion of game theory, or why en passant is important compensation.
As your source says (page 23) “Nothing has yet been said as to the place of this book in the history of chess, and, indeed, it must be confessed that it has very little
practical bearing on the game.”
Caxton actually doesn’t mention en passant at all (which suggests that it postdates him) or game theory (which postdates him by almost 500 years). The book also was written before the queen’s and bishop’s power was increased.
Like one commentator said:
It’s still an interesting historical curiousity, though.
No worries. I think it’s great that this board is frequented by so many experts on different topics. Next time I see you posting in a chess thread I’ll know to pay attention instead of stupidly trying to “explain” something. 
Oh come now, glee. Threat is stronger than the execution. And En Passant doesn’t just factor into passed pawns. There’s a line of the King’s Indian that involves Black playing Nd7 and white plays d5. Sooner or later, …a5 is played. Sure, I’d like to play a3 and b4 as white but I can’t since a3 is answered by …a4, locking things up. Why does this lock it up? En passant, of course. b4 would be a great retort if not for …axb3 ep. When you say you use ep in only 1/500 games, I’m sure you only mean you *play *it in 1 of 500. I bet it comes into consideration more than you realize.
I justify e.p. by saying that a pawn’s job is to watch over the other pawns. You can’t have passers, backwards pawns, good bishops, or open files without the enemy pawns being there too. A Rook’s job isn’t to watch pawns, though, so only the pawn gets the special privilege of taking ep.
Chessic Sense, poster formally known as IntelSoldier
[I’ve been posting in four or five military threads since the name change. I felt like my comments were weaker. Nice to have this to balance it out.]
I don’t believe this to be the case. The double space initial pawn move rule could have been introduced to speed up the game without disrupting the relative strength of the pieces. They might not have particularly cared about whether the actual result of the game should be the same or not.
Think about it rationally here. To move 4 spaces with pawns before the double move rule would have taken 4 moves. To move 3 spaces with pawns would have taken 3 moves. To move 4 spaces with pawns now requires 2 moves minimum. To move 3 spaces with pawns requires 2 moves minimum. The ratio of pawn movement to turns required was NOT universally altered by the double move rule, so the intent of the makers of the rule couldn’t have possibly been to ensure the outcome of the game would be no different with a double move. The intent of the rule was to speed up the game without unbalancing the strength of the pieces relative to each other. So in order to prevent pawns from being immune to other pawns in certain situations, en passant was introduced to balance it.
That’s my best guess, at least. I’m not a chess expert or a chess historian.
You are right that there is a standard manouvre in the King’s Indian where White has to play b3 first then a3 and finally b4 (losing one tempo) to avoid Black being able to use en passant.
There’s also a line in the c3 Sicilian where White usually answers …d7-d5 with e5xd6 en passant.
But there are hundreds of opening lines where no en passant occurs (or could occur).
Note also that the King’s Indian capture is nowhere near the centre.
I did indeed mean I play en passant about 1 in 500 games (that’s why I said ‘use’).
So my point that ‘en passant doesn’t add much to a pawn’s value, and has nothing to do with capturing towards the centre’ stands.
Nah. :o
“You can’t have passers, backwards pawns, good bishops, or open files without the enemy pawns being there too” is completely wrong! :smack:
(You can’t have passed pawns if blocking enemy pawns are present; you can’t have open files if any pawn is present; you can have a backward pawn with no enemy pawn anywhere near it and the good bishop is determined by your pawns, not your opponents.)
In a Rook and pawn ending, particularly with only a few pawns left, the Rook’s main job is to watch enemy pawns (with a side order of keeping the enemy King out of play)
Pawns are the soul of chess. -Philidor
The Dovble-Pawn mowe hight ywis broken. Yffe they hath not fixed thys in the next patche, i shalle quitte.
And knockketh the chesse boyard off yhe tayble splaying the peple and nobles upon yhe floore.