Chess Question:

Can we create a legal chess problem position (With a stipulation of white mates in 2) in which all 32 pieces are still present on the board and with the first move as an en passant key?

That sounds really tough, but would be a cool puzzle. 

here you go, white to move, all pieces on board, first move is en passant and its mate in two. 

is chess legal in this country???

if it is not send me to jail

ha, I messed up the puzzle lol. made wrong person to move. 

lol

For those not familiar with chess problem conventions, an en passant capture as the first move is legal ONLY if it could be proved by retro-analysis that Black's last move must have been the pawn double-step and nothing else. In the position below, Black's only possible last move was ...f7-f5, so the e.p. key is legal. The last move wasn't ...f6-f5 because that would imply White was in check while it was Black's turn. It wasn't ...Nf7-h8 for a similar reason. Why couldn't Black have just moved the king to e6?

EDIT 2: Improved setting with 2 extra variations and additional theme thrown in.

Rocky64, that is a lovely puzzle. I think it would be slightly better if the knight was not on b6. That way the knight on f6 was actually neccessary to cover d5. I have the same kind of concern for the bishop on c7. 

I generally appreciate mates that involve as many pieces as possible. But have no square controlled by more than one attacking piece. 

On any square the black king could have moved from, it would be in an impossible double check or in check from a knight with no square from which to make a checking move.

I don't understand where jdcannon is suggesting the white knights should be other than where you have them.

Do you plan to post a proof game for your position?

But jdcannon's solution was unsound because Black could have reached the problem position with a move other than e5, making the en passant capture illegal.

No it's not. Read #8 again about what makes an e.p. capture legal in a composition.

We do know the move might have been something besides a double step of Black's e-pawn. That disallows the e.p. capture. Read #8 again.

Thanks, but just about every piece has to be exactly where it is for the problem to work. The N on b6 serves multiple purposes: 1. It legitimise the e.p. key by ensuring that ...Kd5-e6 or ...Qb6-b5 wasn't the last move. 2. It guards d5 so that White can actually mate in some variations, e.g. 1...h6+ 2.Nxh6. 3. It makes the Fleck theme possible by forcing 2.Ne3 after 1...Qxb6. There are similar multiple reasons for the B on c7.

That's correct - good job! I'm not planning to make a proof game as it's fairly obvious the position is legal.

I assumed that by "legal chess problem position" the OP meant one that would qualify as a valid composition under the Codex for Chess Composition. But in these forums people sometimes use "problem" and "puzzle" interchangeably, so my assumption might not be justified. If the task was merely to find a position with mate in two after an e.p. capture that might be possible, jdcannon's position would work, but it's a rather trivial task. Requiring the position to be a valid composition makes the task much more difficult, so Rocky64's position is a significant achievement.