Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nc6/3. Bb5/3...a6/4. Ba4

=Ruy Lopez, Morphy Defence= The last two moves ...a6 and Ba4 have made no substantial change to the position, therefore Black's options are much the same as they were on his previous move, although they are now known as deferred defences.

4...Nf6 is the most often played move and is referred to as the main line (rather than the Berlin Deferred). It attacks White's currently undefended e-pawn and helps prepare kingside castling.

4...d6 is the Steinitz Deferred. Much more popular than the true Steinitz Defence, it cuts out any threats to the e-pawn and reserves the option of an f5 push.

4...Bc5 is the Classical Defence Deferred. It develops a piece and controls the a7-g1 diagonal.

Hunting down White's bishop now is not wise. Black can play 4...b5 5.Bb3 Na5, hunting down White's light-squared bishop, however, this takes a lot of time, and after 6.O-O Nxb3 7.axb3, Black is far behind in development. The game Pavlovic-Agdestein, 2003 continued (after 5...Na5) 6.O-O d6 7.d4 f6 (holding on to e5 is Black's main idea in the Ruy Lopez) 8.Nc3 Nxb3 9.axb3 (Black doesn't have one piece off the back rank). Now, White can attack after Bb7 Qe2 g6 Be3 c6 dxe5 fxe5 Ng5 Be7 f4! opening more lines.

Theory table
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 * 1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Ba4