Garry Kasparov had to grind his teeth in his WCh match in the year 2000, since he was unable to win a single game with White against Vladimir Kramnik’s Berlin Defence. The latter then received the nickname of the Berlin Wall. As a result 3...Nf6 against the Ruy Lopez also became ever more popular amongst other grandmasters and the analytical efforts were stepped up in order to find for White some sort of promising setup against this super-solid defence.
3...Nf6 attacks White’s e-pawn, and if White wants to get something out of the position theory recommends rapid development with 4.0-0. On the other hand, the defensive move 4.d3 is of course playable and solid, but certainly not the best theoretical reply. But one advantage of this modest move is that it avoids the queenless middlegame of the main variation. After 4.0-0 Black can capture the e-pawn with the logical 4...Nxe4 (but there is an alternative move in 4...Bc5, which has occasionally been played by Topalov).
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