The King's Gambit [C30-39]
Not exactly the height of fashion these last few decades but still a dangerous weapon if Black isn't well prepared.
A good example being this month's Game 1. White's opening can be found in old books where Black's game is approved by theoreticians, but it can be uncomfortable to navigate such murky positions if you lack the necessary experience:
In the game Black won the exchange but was probably not better as a result. Later on the simplification 24...Nxb3 was both a positional and tactical error.
The Philidor/Lion Defence [C41]
Although the Philidor arises officially via 1 e4 e5 2 Nf3 d6, there is a certain tendency to play a type of Philidor via the Lion (1 e4 d6 2 d4 Nf6 3 Nc3 and now either 3...e5 4 Nf3 Nbd7, as in Game 2, or even 3...Nbd7 first and then 4...e5).
So although the Lion system technically starts as a type of Pirc defence, the intention is generally to obtain a Phildor Defence whilst avoiding various sidelines. For instance after the Philidor move order 1 e4 e5 2 Nf3 d6 3 d4 Nf6, apart from the standard 4 Nc3, White has the slightly annoying 4 dxe5!?.
If we focus our attention on Game 2, then in the diagram position Smerdon reacts with the aggressive move 5 g4. He is then able to keep the advantage and goes on to win a convincing game against Gagunashvili. This move has created problems for Black in recent years and this example illustrates why it continues to do so!
If you like playing this system as Black you'll need to have a closer look at 5 g4 because it's attracting more and more advocates.
Petroff's Defence [C42-3]
In Game 3 young Romain Edouard was able to show that 14 Rxb7 in the following position can be dangerous:
This is somewhat surprising as 14 Rb5 has been played so often it has become almost automatic and yet probably doesn't give any advantage according to established theory.
From the diagram, after 14 Rxb7 Nb6 15 Qc2 I believe that Libiszewski's 15...Bg6 is inferior and that Black should prefer 15...Bxf3 with complications that should be at least playable.
Olivier Renet (your very own 1 e4 e5 specialist in recent years) recommended 14 Rxb7 in an earlier update and has worked with Romain Edouard, so it's perhaps no surprise that the European U-16 champion used this idea.
Another very theoretical line is featured in Game 4. The notes show that there have been a number of new ideas introduced in the quest by White players seeking something concrete from the opening.
The actual game is one-sided as Black first avoided 17...Na5 (has anyone found an improvement on Kramnik's game against Leko which turned out fine for Black?) and was then a shade worse. Later he blundered a big pawn and lost without resisting very well.
Black employs the 5...Nd7 system in the next two games with mixed results:
In Game 5 Karpatchev temporarily sacrifices a pawn in a slightly unusual way. When he finally recovered the material he was faced with a loss of central control. White's central pawns pushing Black's pieces out of the way.
Despite the fact that it's well-known, and often plays out to a draw, I'm fairly sure that 10...Nxc3 is safer than 10...cxd5.
As light relief from all the heavy theory in this month's update of the Petroff comes Game 6. Yusupov (I prefer this spelling!) rocks Mr. Can with a fine piece sacrifice which in my opinion is sound and worth at least a draw. This game and the notes have rather put me off 8 Qh5. So Game 5 is the most significant if White is looking for an edge.
The Four Knights [C48]
There are three games from the Rubinstein (4...Nd4) variation and one with the unnamed 4...Bd6.
In this well-known position from the Rubinstein, most players will automatically play 8...Ne8, but in Game 7 Carlsen tried 8...c6 against Motylev in this year's Wijk aan Zee A-tournament. Although this isn't a novelty it's a rare enough move to surprise many! The piece offer has yet to be accepted but it will certainly be interesting to see if White can grab it, survive and thrive. Watch this space for news on this one.
In the game, Motylev's 9 0-0 was safe enough but he failed to obtain any advantage. Only later did young Carlsen go wrong allowing the bishops to create unpleasant threats. Later on, in time trouble (I presume), Motylev went astray and even found himself the exchange down only to spring into action and find a neat combination to earn a draw.
Dropping back to c4 with the bishop is another popular option. In Game 8 Black then replied with 5...d6 following Kramnik, but 5...Bd6 and 5...c6 are more critical theoretically and (on the evidence of the notes that I've added to the game) doing well for Black.
The other way of gambiting against 5 Ba4 is 5...c6 which was employed in Shanava-Khenkin, Game 9:
As so often happens in this line, Black stays a pawn down for quite some time but White has doubled and isolated f-pawns which ensures Black plenty of practical compensation. Recent experience seems to suggest that White has as much to fear as Black in the resulting tense middlegames, so I expect 5...c6 to be continue to be played by 2600+ players.
A practical way to avoid the rigours of Four Knight's theory is to play 5...Bd6:
This slightly ugly-looking move has been played by a number of Grandmasters but in Game 10 it is tested at 2700-level. Unfortunately Sasikiran doesn't handle the late-opening that well and is soon in trouble, but the notes suggest a number of alternatives and improvements for Black.
With the Four Knights becoming a regular at top-class chess tournaments the surprise value of this opening has gone. The theory is rich and evolving very fast and so there is a good chance that we will come back to this reinvigorated opening in the coming months.