# Why is it a good idea to fianchetto above the castled King? If I do that, should I make sure to leave the Bishop there for a while to guard the hole?

I understand why fianchettoing can be helpful, even deadly to an opponent, but should it really be done on the side which the King castles into? I realize that the King's Indian Defense/Attack involves fianchettoing on the kingside as well as castling to the kingside, for Black and White respectively; and that that position is quite strong. But I'd like to know the principle behind opening up the N-pawn above the castled King. Is it a weak point? And if so, should I be careful not to move my Bishop from the fianchetto square?

I suppose more generally my question is: what should I be careful of when advancing a pawn in front of a castled King in the early to middle game?

Fianchettoes are a very common and strong setup. But watch also for the 2 most common attacks against a fianchettoed position, which are:

A. Launching the rook pawn up the board (against Black this would be h4-h5 etc.) and opening up the h-file. I have played this many times against the Pirc where Black "castles into" the attack. White plays h4-h5 followed by trading off the pawn and then plays Qh6+ with a very strong attack down the open file.

B. The sacrifice of a knight on f5 (where Black accepting the sac would play ...gxf5). This wrenches open the position and jacks up the pawn structure.

Even if the opponent trades his same-color bishop for your fianchettoed bishop, you can still become weak on that color complex (e.g. the opponent's queen can roost on h6 for example and be a thorn in your side)

What should you be careful of? Losing the fianchettoed bishop while your opponent has that colored bishop and the Q. You'll probably find all sorts of players who'd trade a rook for that bishop.

Keep the bishop on the long diagonal unless there's a compelling reason not to.

Defensively, the bishop is pretty good. Offensively, it shoots through the middle of the board, peeks the opponent's rook and knight pawn, and sometimes adds pressure to the enemy K, depending on how the castling goes.

The advantage of a fianchetto (for defense) is that it is a "super pawn" in front of your king. It also has offensive value in controlling two squares of the center.

The danger is that it can be exchanged. If you have a rook on f1 (f8) and a bishop on g2 (g7), the opposing bishop could go to the square on the h file, supported by his queen, pinning your bishop. So you need to be careful to move the rook so that your bishop can retreat to h1 (h8).

The other thing to be aware of is the potential for a knight sacrifice at f4 (f5) that threatens to remove either the bishop, or at least the g-pawn in front of it.