I'm an early intermediate player, so forgive me if this is a simple question. This is also my first post on this site.

I sometimes see a4 played by white but I do not know what kind of plan this move suggests. What does a4 do? Is a4 an aggressive move, or a passive move?

If it helps, a4 is a viable option in the following early position:



What does an a4 move in this position do, as opposed to the more standard-looking moves of d3, or O-O?

I have not seen your set up. But it depends on the position. Wing pawn moves like a4 or h4 have purposes, it just depends on the chess position. These are the possible reasons of a4 move.

1. Stop or slowdown your enemy' queenside activity.
2. Provoke a weakness on your opponent's queenside. Which can give you active piece play there.
3. Fix a weakness there.
4. Possible tactical blows.
5. If the position has an opposite side castling. Your opponent wants to open the position there for his rooks to pressure your king.

In the position you posted....... I think White has better moves here than a4.
You are right: d3 and 0-0 are better!!! a4 doesn't do much here.

In General, the move a4, should not be heavily considered in the opening because: piece development takes priority over that and it is not a threatening move, capturing move, protecting move, flight move, trapping move, or blocking move. (I personally developed these Concepts), which can be applied here.

I hope this helps!

Sincerely,

dustinkinney.

Well, a4 has another strong purpose here, simply based on the fact that the King's rook is on f8. (This is actually a very good example of a "Positional Consideration".)

Black's King appears to be in worse shape than White's. Therefore, White wants to exploit this by opening-up the Queenside, thereby weakening Black's King even more.

In my opinion, of course.

Oh, and welcome Glenn!

Shouldn't piece development take priority first? This is the opening!
I mean, Launching a queenside attack on Black's king, since Black decided not to castle king-side is a possibility, but first, shouldn't NORMAL play continue to allow White more options? He can allways play a4 later. Isn't white's plan with a4 slower, initially, and he should first bring more pieces to bear? Because of Priority......

Explain your Opinion, Please..... Perhaps, I can learn something new.

Well, yes. Normally. Note the placement of the rook at f8? This is not normal opening development, right?

d3, and 0-0, are absolutely, not better. White has time here, why waste it? Can you tell us one reason why White needs to castle here immediately?

In order to exploit the breaking of opening rules, you often have to break them yourself.

On the surface, this statement might seem shallow...

I 100% agree with this assessment of the move. It is especially popular in blitz and bullet matches. What white is saying is, "I know now that you cannot castle kingside, so you'll probably go queenside if you do in fact castle, so I think I'll shove the a pawn in that general direction - maybe keep your king in the middle longer!"

SO, to answer the question, "Isn't piece development more important in the opening?" - YES, of course, but as was brought up, Rf8 is NOT a normal opening move, and therefore staying in "book" might be wacky here, as well.

Remember, play the position, play the board! If someone continues to develop pieces when there is a mate in the air because of the opponent's blunder, then it's kinda silly, yea?

Hope this helps. a4 is a psychological, as well as space-gaining, move in my opinion!