4...Bc5 5.Bxc6 dxc6 6.d3 O-O (or 6...Bd6) 7.h3!? (Pinski) 7...Bd6!? and does White has an advantage? Usually the Nc3 beongs on c4 (Nbd2-Nc4 is played in those structures) so i don't really believe that this extra White's tempo (Nb1-Nc3) over the delayed exchange Spanish variation is a great gain. Black will continue with b6+c5+Nd7+Nb8 as usual and even if somehow White gets an edge it will not be significant and even then Black can play for the win, so 4...Bc5 is a winning attempt after all. Dvoretsky in his "Analytical Manual" also expresses the same opinion.

4...Bd6 5.d3 a6 6.Ba4 h6 7.a3! b5 (7...O-O 8.g4!) 8.Bb3 Bb7 9.Be3! is the clever sequence given by Emms and i haven't found a way to combat it yet.

I fed Houdini last night with the position after 4...Bc5 5.O-O
(5.Bxc6 dxc6 6.d3 is critical and better for White according to Pinski. I'm not sure about that but there is a problem when White plays Be3. Black probably has to play ...Bd6 and lose a tempo compared with those delayed exchange spanish variations)
5...O-O 6.Nxe5 Nxe5 7.d4 Bd6 8.f4 Nc6 9.e5 Be7 10.d5 Nb4 11.exf6 Bxf6 and after some hours of analysis it thought that Black is absolutely equal (< 0.10 is all variations). I can post some analysis if someone is interested.

Plus there's a move order issue I brought up in another thread, related to the fact that White (ok, he may not be this clever) can play 2.Nc3 before Nf3. The strongest way to combat this move would be to play Nf6 in order to get d5, in particularly against the Vienna Gambit. Gusta also recommends the Nf6 and d5 plan against the g3 Vienna. But if you play this then the g6 plan is out. 2...Nc6 can be punished with a better version of the Vienna Gambit with 3.f4 as played against Kosteniuk by Ivanchuk, for example.

Not 100% sound i'm afraid. For example look at NCO's suggestion against it and use a PC to analyse this exact line. Black seems not to be in best shape!

Against this Emms gives a fine recommendation again in the DW 1.e4 e5 book

In the Spanish 4 Knights Gus gives 1.e4 e5 2.Nf3 Nc6 3.Nc3 Nf6 4.Bb5 Nd4!? but in the variation recommended by GM Emms in the "Dangerous Weapons: 1.e4 e5" book 5.O-O! Nxb5 6.Nxb5 c6 7.Nc3 d6 8.d4 Qc7 he just says that it is equal but Black has the potential to become better because of the 2 Bishops. This lines seems to have many similarities with some Trompowky lines where White gives the B-pair to gain superiority in the center. Here White plays a4+h3+Re1+Qd3 probably and i quite like his chances for a slight opening advantage as GM Emms does also. So i believe that Gus had to give something more here to persuade us that Black is fully OK.

The thing with the Spanish 4 Knights is that i don't want to give White chances to kill the game quickly. For example 4.Bb5 Nd4 5.Nxd4+e5 is the "famous drawing variation" and after 4...Bb4 5.Bxc6 now or after 5.O-O O-O 6.Bxc5+Nxe5 is the other "famous drawing variation". So, i want to study 4...Bc5!? which seems not to allow these "dead draw" situations. I see at Dvoretsky's Analytical manual the variation 5.Nxe5 Nxe5 6.d4 Bd6 7.f4 Nc6! 8.e5 Bb4 9.d5 Ne4 10.Qd3 Nxc3 11.bxc3 and now 11...Be7= and 11...Ba5!=/+ (Dvoretsky) while there is also 9...Qe7!? But the "problem" is that White usually plays first 5.O-O! and after 5...O-O 6.Nxe5 which i have never face in practice till now and to be honest i really haven't studied it and i don't know what to do. Probably because no strong opponent has played the 4 knights against me untill now (i have faced only 6.d3 and 6.Bxc6 from weak opponents).

So, after 6.Nxe5 Nxe5 7.d4 Bd6 8.f4 Nc6 9.e5 i see that 9...Be7 is the main line but what is wrong with 9...Bb4 as in the above "Dvoretsky line"? So, after 9...Be7 10.d5 Nb4 11.exf6 Bxf6 12.Bc4! was recommended by GM Emms in the DW book and 12...c6 13.d6 Qb6 14.Kh1 Qd4 is what my PC suggests here.

Is out there an expert on this variation to give us his lights? I know that Markovich has some analysis in his old Hard Chess page but i guess that some lines are dated nowdays. In general, do you think that 4...Bc5 is OK for Black in theory?

On the KG-remarks


1. e4 e5 2. f4 exf4 3. Nf3 g5 4. h4 g4 5. Ne5 Nf6 6. Bc4 d5 7. exd5 Bd6 8. d4 Nh5 9. Nc3 0-0 



Now:

10.Ne2?! was refuted on the chesspubsite by Craig Evans in 2008:. The lines are exactly the same as those provided by Gustafsson, so sorry but nothing new there. 
Subscribers to the Chesspub 1.e4,e5 area, might have pulled them out of my 2009 KG-Survey.

10....Qe7! with the point that 
11.Nxf4,Ng3! (Craig Evens confirmed by Buecker)
and 
11.0-0 f3! (Buecker)

10.Ne4! (recommended by Jon Tait is best. Heavy analytic work on these lines was carried out by Michael Jenssen, David Flude - who provided some key ideas and mostly by Stephan Buecker)
10.....Re8! (10....f5 is very complex and offers White good winning chances according to Kaissiber 32,33/Buecker)
[11] 0-0!,Bxe5
[12] dxe5,Rxe5
[13]Ng5           (Hanison Lomis, quoted by Jon Tait)
[13]       , Qd6! iso 13...h6? played by Loomis
[14]Qd4,Nc6
[15]Qf2,
[15]      ,Nb4  15....Ne7!= (Was the first recommendation in my KG-survey for chesspub )
[16]Bxf4,Nxf4
[17]Qxf4,Bf5
[18]Rad1

[18]      , Nxc2!
With the point
19.Nxf7,Kxg7 20.Bd3,Ne3=
This was my second improvement over the Kaissiber-analysis.
I published it at the beginning of 2009 in my KG survey for Chesspub (subscribers area where it still can be downloaded)
Both improvements have been confirmed in corr. games since 2009.

Only 18....h6? was cited in Kaissiber (Eberl-Kayis, ICCF, 2007)



My own take on this is that Black is OK in this line, as long as he knows what he is doing.
Personally I prefer to answer Bc4,d5 exd5 with the old ....Bg7 over Bd6.