I share your interest in the Tango and hope that someday soon it might be properly covered on ChessPub. I’ve often wondered how theory has moved on since Orlov’s ’98 book.

A ChessBase/ChessLive search doesn’t seem to throw up much that’s new in the 3 Nf3 e6 4 a3 d6 lines, though I did find a few new ideas. (Please treat the following as a general indication only, though, as I’m not a strong player!) After 5 Nc3 g6 6 e4 Bg7 7 Be2 0-0 8 0-0 Black has tried a number of moves other than 8 …Re8, which I assume leads to a White edge after 9 Be3 e5 10 d5 Nd4 11 Re1, but are they any better? No less a player than Vlassov has tried 8 …e5, which looked odd to me at first since in the 9 Nd2 a5 KID, a3 is a vital move, but maybe the idea is that after 9 d5 Ne7 10 Nd2 here Black might switch to the ...c5 plan where a2-a3 might not be so useful? 8 …h6 and 8 …Nd7 have also been played, presumably in the hope that White won’t have many useful ‘KID’ moves before Black plays …e5. Maybe after 8 …Nd7, d5 can sometimes be met by …Nd4, but is either try really convincing?

The 4 …d5 lines don’t, it’s true, seem very popular. I don’t myself like 4 …d5 5 Nc3 g6 because of 6 Bg5 Bg7 7 e3 h6 8 Bf6 Bf6 9 cd ed 10 Bb5, but isn’t Orlov’s 5 …Be7 reasonable here? -- e.g. 6 Bg5 h6 7 Bh4 Ne4 (7 …a6!? has been seen a couple of times, and obviously …dc!? is a try too) 8 Be7 Ne7!? (8 ...Qe7!?) 9 e3 0-0; or alternatively 6 …dc 7 e3 Na5 (7 …Nd5 is playable but a bit better for White after 8 Be7?) 8 Nd2, and here Orlov gives 8 …c5 but what’s wrong with simply 8 …0-0, transposing to the game Kuhlmann-Simmelink but without …h6/Bh4 thrown in? These lines might be a bit boring, but maybe it’s logical to play on the light squares with …d5/…dxc4 after White has slightly weakened them with a2-a3?

When I wrote this post a couple of days ago I forgot that Vlassov has also tried 4 …g6 on seven occasions (registering four draws and three losses!). This can transpose to 4 …d6 lines, but Vlassov’s idea was, after 5 Nc3 (5 d5 presumably just transposes) Bg7 6 e4 (6 d5 Ne7 7 e4 0-0 8 Be2 d6 9 0-0 e5 leads to the same tempo-down KID as 4 …d6 can, though in Khurtsidze-Vlassov White preferred 9 de fe 10 e5), to try a kind of Grünfeld setup with 6 …d5!? 7 e5 (7 Bg5!?) Ne4 8 Bd3 Nc3 9 bc Na5. (After this, just on a whim I searched for the ridiculous-looking 4 …b6?!, and found it had actually been played, by - of course! - Tony Miles, though from a Queen’s Indian move order. After 5 Nc3 d5?! 6 cd ed 7 Bf4? a6 8 e3 Bd6 9 Bd6 Qd6 a draw was agreed, but after 7 Bg5 Black might have needed a spot of ingenuity to get out of the opening alive ...)

I’d really appreciate your views on all this, and also on what I take to be perhaps the biggest challenge to the Tango, namely 3 Nc3 e5 4 d5 Ne7 5 h4. After 5 …Neg8 (I presume Orlov’s 5 …g6 is bad, if only because of 6 Bg5 Bg7 7 d6 Nf5 8 e4) 6 a3, 6 …a5 has been tried a number of times as well as 6 …a6. (Orlov says 6 …Bc5 runs into 7 Na4, but is 7 …Be7, perhaps intending a quick …c6, clearly bad?) One of Orlov’s main lines is 6 ...a6 7 Nf3 Ng4 8 e3 f5 9 Be2 Ngf6 10 Qc2 d6 11 Ng5 Qe7 which he concedes is better for White, but with the pawn on a5 can’t Black meet 9 Be2 here with 9 ...Bc5 (or 9 Qc2 N8h6 then ...Bc5), immune from b4/d6 thrusts?