An interesting question about Evan's gambit.

Good Morning!

I have an interesting question about Evan's gambit. If black taking the b3 pawn in the fourth move with the knight, the engine suggests castling kingside before going to d4 with the pawn, but when the b3 pawn taken by the bishop, going to d4 suggested first.

Can someone explain to me why?

Thank you very much!

https://www.chess.com/openings/Giuoco-Piano-Game-Evans-Gambit

b4 you mean. c3 then d4

Yes, sorry, i forgot to mention than. Do you know the answer for my original question?

Didn't the link explain it?

"White gambits the b4 pawn to gain time attacking the black piece which captures it, and take over the center with c2-c3 and d2-d4."

I'm sorry, i think i asked the question wrong. First of all, i know what is Evan's gambit. Lets analyze it step by step:

1. e4 - e5

2. Nf3 - Nc6

3. Bc4 - Bc5

4. b4 - (and here is my original question)

Black can take the b4 pawn with the bishop or the knight. When the b4 pawn taken with the knight, the engine suggests castling before anything else. When the b4 pawn taken by the bishop, the engine suggests pawn to c3 instead of castling. My main question is why there is difference depending what piece is capturing the b4 pawn.

I'm sorry for asking the question wrong, i was in hurry in the morning and unable explain it correctly.

c3 is the human move in either case.

Which engine are you using?

Stockfish 11

I'm running Stockfish 17 and it's suggesting c3 if black plays 4...Nxb4 or 4...Bxb4. After 1.e4 e5 2.Nf3 Nc6 3.Bc4 Bc5 4.b4 Nxb4 5.0-0 you invite a transposition to the Lasker Defense after 5...d6 6.c3 Nc6 7.d4 Bb6.

For those who like traps, here's one after 4...Nxb4.

As for OP's question, I'm not up on the 4...Nxb4 move because I only play the Evans for black, and in fact I play the Normal Defense: 4...Bxb4 5.c3 Bc5 6.d4 exd4 7.cxd4 Bb6 8.O-O d6. After 5...Bc5!? it makes no difference whether white plays 6.d4 or 6.O-O, they reach the same position, e.g. 6.O-O d6 7.d4 exd4 8.cxd4 Bb6. But if black played 4...Bxb4 5.c3 Ba5 it does make a difference, and theory considers 6.d4 better than 6.O-O.

Now 4...Nxb4 5.c3 Nc6 transposes to the same as the defense I play with 4...Bxb4 5.c3 Bc5. Are you comparing that position with the one after 4...Bxb4 5.c3 Ba5 ?? Again, with the bishop on a5, 6.d4 is better, but with the bishop on c5, 6.d4 and 6.O-O are equally good. If Stockfish 11 reports 6.O-O as "best" there it's not wrong, but it's not right either.

If there's very little difference in engine evaluation between two moves then sometimes it's a little arbitrary (like in chaos theory) which one is reported as "best". There are different ways to check on that difference. For interactive "what if" analysis I like to run an engine with MultiPV = 2, so I can see right away in the analysis pane if there is any difference between the 1st and 2nd best moves. Another way to check is simply to make the two moves and analyze each one in turn, making a note of the evaluation.

Let me start off by saying sometimes in Chess a Chess move can have multiple reasons on why it is played.

I don’t know all the reasons on why Castling is better vs. playing c3.

However, I do believe I know 1 possible reason.

I think the reason White wants to castle is so White can take the e5 pawn while side stepping a tactic.

——————————————————

1 Difference between taking the b4 pawn with the Knight vs. the Bishop is the E5 pawn.

The Knight on c6 is the only defender of the E5 pawn. So when Black takes on b4 with Knight, It opens up the possibility for White Knight on f3 to capture the E5 pawn.

However, A Tactic prevents White from doing it right away!

I will show the tactic in an example:

So in this position - White is giving up the B4 pawn. Black decides to take with Knight removing the E5 pawn defender.

If White rushes to take E5 pawn, you can see the trouble white faces.

The Knight on e5 is undefended and if it moves the Rook on a1 is undefended.

In addition, If White played move like Bb2 trying to defend the Knight it would help because of a Checkmate idea Black has.

So I believe the move Castles is White Clever way of Side Stepping the Tactic + keeping an Eye on E5 pawn.

If Black doesn’t pay attention, White might be able to grab it.

For Example:

Now you can notice a difference with King Castled Black doesn’t have similar tricks!

Thank you very much for your answers!