Dragon Variation, Yugoslav Attack, Modern Line

In the Modern Line, White castles queenside on move 9 instead of spending a tempo on 9. Bc4 or advancing with 9. g4. Castling first speeds up the attack with Bh6, h4-h5 and g4, and it keeps the light-squared bishop off c4, where it would be a target on the c-file. The cost is that nothing stops the freeing 9...d5, which strikes at e4 straight away and lets Black dispute the center before the kingside storm gathers pace.

That counterblow is Black's most common answer and its best-scoring one in the database; it also heads the engine's preferences. The more traditional 9...Bd7, preparing ...Rc8 and play along the c-file, is the second choice and fares noticeably worse for Black. 9...Nxd4, removing the centralized knight before choosing a plan, comes next. The engine also suggests 9...h5 and 9...Qa5. It gives White a slight edge in the starting position, while overall results are close to balanced, with a small majority of decisive games going White's way.