K - King safety; always a good place to start--he who is mated last, wins first. Huh? Oh, okay, that makes sense...beat the other guy to the punch and bloody up his King, IF it can be done. Otherwise, find something else to do! There are ways to win besides blindly chasing the other player's King.
A simple system for evaluating each element of KIMPLODES
KIMPLODES offers a structured way to think about your game, and may show you a way to think during a game so that you save time and consider important points. In post-game analysis it offers a way to evaluate each factor based on KIMPLODES and determine which factors were most important, so that in the future you are more likely to recognize the key features in a game while playing.
Basically, I look at each element of KIMPLODES and use my own variants of standard chess notation (shown below) to make an assessment. Then you can subjectively "add them up" (I don't recommend that), or you can determine what you want to do based on which elements you determined are the most important in a given position--this takes practice, practice, practice...(blah, blah, blah...you've heard it before, and it's still true. It's up to you to determine if the benefit is worth the investment in time.)
+- White has a significant, perhaps winning edge; +/- White has an edge; +/= White has a slight edge; = neither side has an apparent edge; or "U" for unclear (when I just don't know)
-+ Black has a significant, perhaps winning edge; -/+ Black has an edge; =/+ Black has a slight edge; = neither side has an apparent edge; or "U" for unclear (when I just don't know)
You can make up your own notation, I just recommend keeping it simple.
King safety: basic building blocks.
Black's King safety is the most important feature in the above position, as White threatens to play Qxf7#. At the moment Black should look at this position and think, "The K factor is +-. That's very bad. What should I do?. Oh, of course. I Develop a piece with ... Nf6, the K factor goes to =, and White's Queen looks kind of stupid sitting on f3 and blocking the Knight on g1."
A cheesy example, but it reduces the problem to essentials.
In the above diagram, neither King's safety is particularly relevant at the moment (the evaluation of K factor is =). The Queens are off the board, and both Kings will castle easily. Things may heat up later, but at the moment, the King's safety isn't what should be driving thinking on how the game should proceed. Instead White is hoping to take advantage of his undamaged K-side majority (remove all the pieces, and White would have a significant edge in the pawn endgame), and Black plans to use his Bishop pair to cause a transformation in the position that will lead to some other advantage as the game proceeds.
Can King safety be the most important factor for both sides? "Yes", is the simplest answer! In the above position it is White to move (K factor +-), and he wins by force as long as he continually checks Black. One non-check and the K factor switches to -+ and Black will checkmate White instead. Is that realistic? To quote the 3 Stooges, "Certainly!" In a more complex position, it is not uncommon for the side that wastes a single tempo to lose the game, as happens in many Sicilians with opposite side castling and attacks. That is why it is important to look not just at your opponent's King safety, but your own. If your opponent can mate you on his next move unless you destroy one of his pieces, mate him instead, move out of the way, or intervene, it provides a terrible motivation to focus on whether or not you can survive.
King safety in the opening
When King safety matters in the opening
In the Caro-Kann variation shown above, White's focus is on making the Black's King position insecure. As a result, the K factor stays at +/= from move 5 until some point in the middle game...and that evaluation can switch swiftly to +- if Black is not careful, or is simply unaware of some of the tricks, traps and tactics available to White. Other openings where the King factor can rapidly shift off the = peg: Kings Gambit; Schliemann variation of Ruy Lopez.
When King safety doesn't matter in the opening
As MCO-15 notes (p. 724), "The King's Indian Attack is not, strictly speaking, an opening, but a path for White to follow regardless of Black's opening moves. As the setup is a compact structure on White's side of the board, Black cannot prevent it without unreasonable play." The position above looks at two normal lines in the KIA through move 8. In both cases King safety is not a factor in the opening. Other openings where the King factor tends to stay centered on = during the opening: Queens Gambit Declined; Ruy Lopez. Even here there will be exceptions.
King safety in the middle game
When King safety matters in the middle game
There are certain middle games in which King safety is a crucial factor that must be considered by both players on every move. For instance, any opening in which opposite side castling occured often tends to involve ferocious, competing, middle game attacks against the enemy Kings. This frequently occurs in the Sicilian Defense. Another instance in which White often suffers from a King factor of =/+ well into the middle game is the Classical version of the King's Indian Defense, when White hopes that his play on the Q-side will compensate for Black's attack on the K-side (Kramnik has had great success as White).
In the puzzle shown above, the correct K factor is -+, but it takes some serious swashbuckling to bring the point home...this is NOT an easy puzzle for most players (unless you've read all my blogs, for which I tender my condolences, or you are very good, in which case this blog probably offers you very little). CLUE: Mate in 6.
But how do you know the correct K factor is -+? Let's take a look at the starting position after Nxc7?. White's Queen and Knight are offsides, doing nothing to defend His Majesty. The Rook on d1 looks nice...but also is not contributing to the defense. The Rook on f1 is defending f2, as is the King, but in turn Black can apply pressure there with all 4 of his pieces if necessary. That leaves the White King to defend g2 and h2 against Black's Queen, Knight, and any Rook that finds its way to the f or g files. Kind of an unfair fight. Since the King clearly cannot defend the white pawns against those odds, it is clear the pawns will have to move, so that they can block Black pieces and rely upon each other for protection (e.g., after g2-g3 that pawn is protected by the f2 and h2 pawns.) Given a clear majority of useful pieces in the region, all Black has to do is figure out where to sacrifice a piece or pieces to disrupt the pawns that are the only thing standing between all of Black's pieces and the White King. Given that description, would not you too say that Black has a significant, probably winning advantage? I thought so. K factor: -+!
When King safety doesn't matter in the middle game
In the game above, (there are notes included as you play through the game) White elected to trade Queens on move 4 in order to take away Black's right to castle--the problem is that Black's King is perfectly safe (K-factor is =!) as he has an EXTREMELY solid pawn structure that covers all the jumping off points White might ordinarily use to launch an attack. After Black's 7th move, his pawns prevent White pieces from landing on b5, d5, d4, f4 or g5, and there are no ready White pawn breaks to disturb Black's pawns. The result is that Black has an extremely easy endgame to play, while White must consciously exert energy to find a plan. In this game, the consequence was that White overreached and Black handily won a pawn, while still allowing no vulnerabilities to exist on the Black side of the board. This same line with the early queen trade has been played numerous times at the master and above level, and Black has scored extremely well according to IM Lakdawala's review of databases (from his book on the Caro-Kann).
King safety in the endgame
When King safety matters in the endgame
Losing sight of King safety can cost even world champions a game...
How would you reach the evaluation of -+? It's all about the weakened light squares on White's K-side, the lack of defender's, and the fact Black can take advantage of those light squares. It all adds up to K factor -+ after 41 Bc4??, the first move after making the time control.
...so mere mortals, such as myself, can't feel too bad about losing a half point for forgetting about King safety, resulting in the King safety factor switching from =/+ (because the White King is in the center) to -+, so that White barely hangs on (the details are in the notes, as we agreed to a draw since a perpetual check was inevitable with best play, and Black could not try for more as he would be significantly behind in material.) Again, the K factor is -+ because of the weak light squares on White's K-side, exacerbated by the fact White's King is in the middle. If only Anand had lost his game before I reached this position, I would have known better.
When King safety doesn't matter in the endgame
Tactics Trainer on chess.com
Any book with tactics puzzles (preferably with opening, middle game and endgame positions)
Rudolf Spielmann, The Art of Sacrifice in Chess