At the most basic level, White's third move attacks the knight which defends the e5-pawn from the attack by the f3 knight. White's apparent threat to win Black's e-pawn with 4.Bxc6 dxc6 5.Nxe5 is illusory—Black can respond with 5...Qd4, forking the knight and e4-pawn, or 5...Qg5, forking the knight and g2-pawn, both of which win back the material with a good position. White's 3.Bb5 is still a good move, however: it develops a piece, prepares castling, and sets up a potential pin against Black's king. Since White's third move carries no immediate threat, Black can respond in a wide variety of ways.
Traditionally, White's objective in playing the Ruy Lopez is to spoil Black's pawn structure; either way Black recaptures following the exchange on c6 will have negative features for him, though he thereby gains the bishop pair. White does not always exchange bishop for knight on c6, however, but usually in the various forms of the Exchange Variation (ECO C68–C69).
The theory of the Ruy Lopez is the most extensively developed of all open games, with some lines having been analysed well beyond move thirty. At nearly every move there are many reasonable alternatives, and most have been deeply explored. It is convenient to divide the possibilities into two groups based on whether or not Black responds with (3...a6), which is named the Morphy Defence after Paul Morphy, although he was not the originator of the line. The variations with Black moves other than 3...a6 are older and generally simpler, but the Morphy Defence lines are more commonly played.
By far the most commonly played Black third move is the Morphy Defence, 3...a6, which "puts the question" to the white bishop. The main point to 3...a6 is that after the common retreat 4.Ba4, Black will have the possibility of breaking the eventual pin on his queen knight by playing ...b5. White must take some care not to fall into the Noah's Ark Trap, in which Black traps White's king bishop on the b3-square with a ...a6, ...b5, and ...c4 pawn advance on the queenside. Ercole del Rio, in his 1750 treatise Sopra il giuoco degli Scacchi, Osservazioni pratiche dell'anonimo Modenese (On the game of Chess, practical Observations by an anonymous Modenese), was the first author to mention 3...a6. However, the move became popular after it was played by Paul Morphy, and it is named for him. Steinitz did not approve of the move; in 1889, he wrote, "on principle this ought to be disadvantageous as it drives the bishop where it wants to go". Steinitz' opinion did not prevail, however; today, 3...a6 is played in over 75 percent of all games beginning with the Ruy Lopez.
Morphy Defence: alternatives to Closed Defence
After 3...a6, the most commonly played line is the Closed Defence, which goes 4.Ba4 Nf6 5.0-0 Be7, discussed in the two following sections. Alternatives to the Closed Defence described in this section are:
- 4.Bxc6 (Exchange Variation)
- 4...b5 5.Bb3 Na5 (Norwegian Variation)
- 4...b5 5.Bb3 Bc5 (Graz Defence)
- 4...b5 5.Bb3 Bb7
- 4...Bc5 (Classical Defence Deferred)
- 4...d6 (Steinitz Defence Deferred)
- 4...f5 (Schliemann Defence Deferred)
- 4...Nf6 5.0-0 b5 6.Bb3 Bb7 (Arkhangelsk Defence)
- 4...Nf6 5.0-0 b5 6.Bb3 Bc5 (Modern Archangel Defence)
- 4...Nf6 5.0-0 Bc5 (Møller Defence)
- 4...Nf6 5.0-0 d6 (Russian Defence)
- 4...Nf6 5.0-0 Nxe4 (Open Defence)
- 4...Nf6 5.d4
- 4...Nf6 5.Qe2 (Wormald Attack)
- 4...Nf6 5.d3 (Anderssen Variation)
In the Exchange Variation, 4.Bxc6, (ECO C68–C69) White damages Black's pawn structure, giving him a ready-made long-term plan of playing d4 ...exd4 Qxd4, followed by exchanging all the pieces and winning the pure pawn ending. Black gains good compensation, however, in the form of the bishop pair, and the variation is not considered White's most ambitious, though former world champions Emanuel Lasker and Bobby Fischer employed it with success.
After 4.Bxc6, Black almost always responds 4...dxc6, although 4...bxc6 is playable. It is not usually played due to the reply 5.d4 exd4 6.Qxd4 and White is in control of the centre. After 4...dxc6, the obvious 5.Nxe5? is weak, since 5...Qd4! 6.Nf3 Qxe4+ 7.Qe2 Qxe2+ leaves White with no compensation for Black's bishop pair. There are two principal lines after 4.Bxc6 dxc6. In the late 19th and early 20th centuries, Lasker had great success with 5.d4 exd4 6.Qxd4 Qxd4 7.Nxd4. Since then, better defences for Black have been developed, and this line is considered to slightly favour Black. Jon Jacobs wrote in the July 2005 Chess Life (p. 21): "A database search (limited to games longer than 20 moves, both players FIDE 2300+) reveals the position after 7.Nxd4 was reached 20 times from 1985–2002. White's results were abysmal: +0−7=13." Max Euwe gives the pure pawn ending in this position as a win for White.
The flexible 5.0-0 is sometimes called the Barendregt Variation, but it was Fischer who developed it into a serious weapon in the 1960s. Unlike 5.d4, it forces Black to defend his e-pawn, which he usually does with 5...f6, 5...Bg4, 5...Qd6 (the sharpest line, preparing queenside castling), 5...Qe7, 5...Qf6 or 5...Bd6. A rare but playable move is 5...Be6 (or 5...Be7), the idea being that if White plays 6.Nxe5, Black plays 6... Qd4, forking the knight and the e4-pawn. The move ...Qd4, regaining the pawn at e4, is usually impossible in these variations once White has castled, due to the open e-file.
White may also delay the exchange for a move or two: 4.Ba4 Nf6 5.Bxc6 or 5.0-0 Be7 6.Bxc6 (the Delayed Exchange Deferred), for example; at first glance this seems a waste of time, but Black having played ...Nf6 rules out defending the pawn with ...f6, and the bishop already being on e7 means that ...Bd6 would be a loss of tempo.
Variations combining 3...a6 and ...Bc5
The Graz Defence, Classical Defence Deferred, and Møller Defence combine 3...a6 with the active move ...Bc5. For a century it was believed that it was safer for Black to place the bishop on e7, but it is much more active on c5. White can gain time after playing d4 as the black bishop will have to move, but this does not always seem to be as important as was once thought.
The Møller Defence, 3...a6 4.Ba4 Nf6 5.0-0 Bc5 was already an old line in 1903 when Dane Jørgen Møller (1873–1944) analysed it in Tidsskrift för Schack. Alexander Alekhine played this for Black in the early portion of his career; despite his advocacy, it never achieved great popularity, and even he eventually came to consider it dubious.
The Graz Defence, 3...a6 4.Ba4 b5 5.Bb3 Bc5, was analysed by Alois Fink (b. 1910) in Österreichische Schachzeitung in 1956 and in Wiener Schach Nachrichten in 1979, although it did not become popular until the 1990s.
The Norwegian Variation (also called the Wing Variation) (ECO C70), 3...a6 4.Ba4 b5 5.Bb3 Na5 aims to eliminate the white bishop but is generally considered too time-consuming for Black. The usual continuation is 6.0-0 d6 7.d4 Nxb3, but the speculative sacrifice 6.Bxf7+?! Kxf7 7.Nxe5+, which drives the black king out, has been played. However, with accurate play, Black is supposed to be able to consolidate his extra piece.
This defence has been known since the 1880s and was reintroduced in 1901 by Carl Schlechter. In the 1950s, Mark Taimanov played it with some success, though it remained a sideline, as it has to this day. The Norwegian connection was first introduced by Svein Johannessen who played the line from 1957 and later strengthened when Simen Agdestein and some other Norwegian players adopted the variation. In 1995 Jonathan Tisdall published the article "Ruy Lopez. The Norwegian Variation" in New in Chess Yearbook 37.
Steinitz Defence Deferred
In the Steinitz Defence Deferred (also called the Modern Steinitz Defence or the Neo-Steinitz Defence) (ECO C71–C76), Black interpolates 3...a6 4.Ba4 before playing 4...d6, which was frequently played byAlexander Alekhine, José Raúl Capablanca and Paul Keres. The possibility of breaking the pin with a timely ...b5 gives Black more latitude than in the Old Steinitz Defence; in particular, in the Old Steinitz, White can practically force Black to give up his strongpoint at e5, but in the Steinitz Deferred, Black is able to maintain his centre. Most plausible White moves are playable here, including 5.c3, 5.c4, 5.Bxc6, 5.d4, and 5.0-0. The sharpSiesta Variation arises after 5.c3 f5, while a manoeuvring game results from the calmer 5.c3 Bd7 6.d4. The game is also sharp after 5.Bxc6+ bxc6 6.d4 or 5.0-0 Bg4 6.h3 h5. The older lines starting with 5.c4 and 5.d4 are not regarded as testing for Black, though the latter offers a tricky gambit. There are six ECO classifications for the Modern Steinitz. White's responses 5.d4, 5.Nc3, and 5.c4 are included in C71, while 5.0-0 is C72. The delayed exchange 5.Bxc6+ bxc6 6.d4 is C73. C74–C76 all begin with 5.c3. C74 covers 5...Nf6, but primarily focuses on 5...f5 6.exf5 Bxf5 with 7.d4 or 7.0-0. C75's main continuation is 5...Bd7 6.d4 Nge7, the Rubinstein Variation. C76 is characterised by the Black kingside fianchetto 5...Bd7 6.d4 g6.
Schliemann Defence Deferred
The Schliemann Defence Deferred, 3...a6 4.Ba4 f5, is rarely seen, with practically its only top-level appearance being in the 1974 Candidates Final, when Viktor Korchnoi adopted it versusAnatoly Karpov. It is considered inferior to the regular Schliemann, since White can answer effectively with 5.d4! exd4 6.e5.
The Arkhangelsk Defence (or Archangel Defence) (ECO C78) was invented by Soviet theoreticians in the city of Arkhangelsk. The variation begins 3...a6 4.Ba4 Nf6 5.0-0 b5 6.Bb3 Bb7. This line often leads to sharp positions in which Black wagers that the fianchettoed bishop's influence on the centre and kingside will offset Black's delay in castling. White has several options, including attempting to build an ideal pawn centre with c3 and d4, defending the e-pawn with Re1 or simply developing. The Arkhangelsk Defence is tactically justified by Black's ability to meet 7.Ng5 with 7...d5 8.exd5 Nd4! (not 8...Nxd5, when White gets the advantage with 9.Qh5 g6 10.Qf3)
The Russian Defence (ECO C79) can be considered a delayed Steinitz Defence Deferred. With the move order 3...a6 4.Ba4 Nf6 5.0-0 d6, Black waits until White castles before playing ...d6. This can enable Black to avoid some lines in the Steinitz Defence Deferred in which White castles queensidealthough the position of the knight on f6 also precludes Black from supporting the centre with f7–f6. These nuances seem to have little importance today, as neither the Steinitz Defence Deferred nor the Russian Defence have been popular for many years.
Chigorin played the Russian Defence in the 1890s, and later it was adopted by Rubinstein and Alekhine. The last significant use of the Russian Defence was in the 1950s when it was played by some Russian masters.
In the Open Defence, 3...a6 4.Ba4 Nf6 5.0-0 Nxe4, Black tries to make use of the time White will take to regain the pawn to gain a foothold in the centre, with play usually continuing 6.d4 b5 7.Bb3 d5 8.dxe5 Be6. Here 8.Nxe5, once adopted by Fischer, is much less often seen, and Black should equalise after the accurate 8...Nxe5 9.dxe5 c6, which avoids prematurely committing the light-squared bishop and solidly defends d5, often a problem in the Open. The Riga Variation, 6...exd4, is considered inferior; the main line runs 7.Re1 d5 8.Nxd4 Bd6! 9.Nxc6 Bxh2+! 10.Kh1! (10.Kxh2 Qh4+ 11.Kg1 Qxf2+ draws by perpetual check.) Qh4 11.Rxe4+! dxe4 12.Qd8+! Qxd8 13.Nxd8+ Kxd8 14.Kxh2 Be6 (14...f5?? 15.Bg5#!) and now the endgame is considered to favor White after 15.Be3 or Nd2 (but not 15.Nc3 c5!, playing to trap the bishop).
White has a variety of options at move nine, including 9.c3, 9.Be3, 9.Qe2 and 9.Nbd2.
The classical line starts with 9.c3 when Black may choose from 9...Na5, 9...Be7 (the main line), and the aggressive 9...Bc5.
After 9.c3 Bc5 10.Nbd2 0-0 11.Bc2, Black must meet the attack on e4, with the following possibilities from which to choose: 11...f5, 11...Bf5, both of which aim to maintain the strongpoint on e4, or the forcing line 11...Nxf2, introduced by the English amateur Vernon Dilworth.
Today, 9.Be3 Be7 10.c3 is often used to transpose into the main line, 9.c3, while obviating the option of the Dilworth.
An old continuation is 11...f5, when after 12.Nb3 Ba7 13.Nfd4 Nxd4 14.Nxd4 Bxd4 White can gain some advantage with Bogoljubov's 15.Qxd4. Instead, the very sharp La Grande Variante continues 15.cxd4 f4 16.f3 Ng3 17.hxg3 fxg3 18.Qd3 Bf5 19.Qxf5 Rxf5 20.Bxf5 Qh4 21.Bh3 Qxd4+ 22.Kh1 Qxe5, with unclear consequences. Perhaps the most famous game in this variation is Smyslov–Reshevsky, 1945 USSR–USA Radio Match. An analysis of the line had just been published in a Russian chess magazine, and Smyslov was able to follow it to quickly obtain a winning position. Reshevsky had not seen the analysis and he struggled in vain to solve the position over the board with hischess clock running. The Dilworth Variation (or Attack), 11...Nxf2 12.Rxf2 f6 13.exf6 Bxf2+ 14.Kxf2 Qxf6 has scored well for Black, with many traps for the ill-prepared White player. The main line leads to unbalanced endgames which are difficult to play for both sides, though with a strong drawing tendency. Yusupov is one of the few grandmasters to often adopt the Dilworth.
In the Howell Attack (ECO C81), 9.Qe2, White aims for play against d5 after Rd1. The game usually continues 9...Be7 10.Rd1 followed by 10...Nc5 or 10...0-0. Keres played this line several times in the late 1940s, and it is sometimes named after him.
Karpov's move, 9.Nbd2, limits Black's options. In the 1978 Karpov–Korchnoi World Chess Championship match, following 9.Nbd2 Nc5 10.c3 d4 (10...Be7 is an old move that remains popular) Karpov introduced the surprising 11.Ng5!?, a move suggested by his trainer, Igor Zaitsev. If Black takes the knight with 11...Qxg5 White regains the material with 12.Qf3. This variation played a decisive role in a later World Championship match, Kasparov–Anand 1995, when Anand was unable to successfully defend as Black.
Closed Defence 4.Ba4 Nf6 5.0-0 Be7: alternatives to Main Line
In the main line, White normally retreats his bishop with 4.Ba4, when the usual continuation is 4...Nf6 5.0-0 Be7. Black now threatens to win a pawn with 6...b5 followed by 7...Nxe4, so White must respond. Usually White defends the e-pawn with 6.Re1 which, in turn, threatens Black with the loss of a pawn after 7.Bxc6 and 8.Nxe5. Black most commonly averts this threat by driving away the white bishop with 6...b5 7.Bb3, although it is also possible to defend the pawn with 6...d6.
After 4...Nf6 5.0-0 Be7, the most frequently seen continuation is 6.Re1 b5 7.Bb3 d6 8.c3 0-0, discussed in the next section. Examined in this section are the alternatives to the main line:
- 6.Bxc6 (Delayed Exchange Variation Deferred)
- 6.d4 (Centre Attack)
- 6.Qe2 (Worrall Attack)
- 6.Re1 d6 (Averbakh Variation)
- 6.Re1 b5 7.Bb3
- 7...Bb7 (Trajković Variation)
- 7...0-0 8.c3 d5 (Marshall Attack)
Delayed Exchange Variation Deferred
The Delayed Exchange Variation Deferred (or Exchange Variation Doubly Deferred) (ECO C85), 6.Bxc6, loses a tempo compared to the Exchange Variation, though in compensation, the black knight on f6 and bishop on e7 are awkwardly placed. The knight on f6 prevents Black from supporting the e-pawn with f7–f6, and the bishop is somewhat passively posted on e7.
Centre Attack 
The Centre Attack (or Centre Variation) (ECO C84), 6.d4, leads to sharp play. Black can hold the balance, but it is easy to make a misstep
Worrall Attack 
In the Worrall Attack (ECO C86), White substitutes 6.Qe2 for 6.Re1. The idea is that the queen will support the e-pawn leaving the rook free to move to d1 to support the advance of the d-pawn, although there isn't always time for this. Play normally continues 6..b5 7.Bb3 followed by 7...0-0 8.c3 and 8...d5 or 8...d6.
Paul Keres played the line several times. More recently, Sergei Tiviakov has played it, as has Nigel Short, who played it twice in his 1992 match against Anatoly Karpov and won both games.
In the Averbakh Variation (C87), named for Yuri Averbakh, Black defends the threatened e-pawn with 6...d6 instead of driving away the white bishop with the more common 6...b5. This defence shares some similarities with the Modern Steinitz and Russian Defences as Black avoids the ...b5 advance that weakens the queenside. White can reply with either 7.Bxc6 bxc6 8.d4 or 7.c3 Bg4 (it is too late for Black to transpose into the more usual lines of the Closed Defence, because 7...b5 would allow 8.Bc2, saving White a tempo over the two-move sequence Bb3–c2 found in other variations). The pintemporarily prevents White from playing d2–d4. In response, White can either force d4 with 8.h3 Bh5 9.Bxc6 bxc6 10.d4, or postpone d4 for the time being and play 8.d3 followed by manoeuvering the queen knight to the kingside with Nbd2–f1–g3.
Trajković Variation 
An alternative to 7...d6 is 7...Bb7. This is known as the Trajković Variation. Black may sacrifice a pawn with 8.c3 d5 9.exd5 Nxd5 10.Nxe5 Nxe5 11.Rxe5 Nf4.
After 6.Re1 b5 7.Bb3, Black often plays 7...0-0. Here White can play 8.c3, but he has other moves. Alternatives are 8.a4, 8.h3, 8.d4, and 8.d3, which are often called "anti-Marshall" moves.
In the case White does play 8.c3, Black can and often does play 8...d6, which is just the main line in another order. But he can also play 8...d5 for the Marshall Attack.
One of Black's more aggressive alternatives is the Marshall Attack: after 3...a6 4.Ba4 Nf6 5.0-0 Be7 6.Re1 b5 7.Bb3 0-0 8.c3 Black plays the gambit8...d5, sacrificing a pawn. The main line begins with 9.exd5 Nxd5 (9...e4?!, the Herman Steiner variation, is considered weaker) 10.Nxe5 Nxe5 11.Rxe5 c6 (Marshall's original moves, 11...Nf6, and 11...Bb7 are considered inferior, but have also yielded good results at top levels of play for Black. GM Joel Benjamin suggests that 11...Bb7 is inferior due to 12.Qf3). Black will attack and force weaknesses in White's kingside which has been stripped of defenders. White's first decision is whether to play 12.d3 or 12.d4. In either case it is apparent that the move 8.c3 is no longer helpful to White. The Black attack can be quite treacherous for White. Since Black's compensation is based on positional rather than tactical considerations, it is difficult or perhaps impossible to find a refutation, and variations have been analyzed very deeply (sometimes beyond move 30) without coming to a definite determination over the soundness of Black's gambit. The Marshall Attack is a very sharp opening system in which a great amount of theoretical knowledge is vital, and many White players, including Garry Kasparov, avoid it by playing one of the anti-Marshall systems, 8.d4, 8.a4 or 8.h3 instead of 8.c3.
This gambit became famous when Frank James Marshall used it as a prepared variation against José Raúl Capablanca in 1918; nevertheless Capablanca found a way through the complications and won. It is often said that Marshall had kept this gambit a secret for use against Capablanca since his defeat in their 1909 match. The most common counterclaim is that Marshall had used a similar approach in 1917 against Walter Frere, However Edward Winter found: no clear evidence of the date for Frere vs Marshall; several games between 1910 and 1918 where Marshall passed up opportunities to use the Marshall Attack against Capablanca; and an 1893 game that used the same line as in Frere vs Marshall.
Improvements to Black's play were found (Marshall played 11...Nf6!? originally, but later discovered 11...c6!) and the Marshall Attack was adopted by top players including Boris Spassky, John Nunn and more recently Michael Adams. In the Classical World Chess Championship 2004, challenger Peter Leko used the Marshall to win an important game against champion Vladimir Kramnik. Currently, Armenian Grandmaster Levon Aronian is one of the main advocates for the Marshall Attack.
Main Line: 4.Ba4 Nf6 5.0-0 Be7 6.Re1 b5 7.Bb3 d6 8.c3 0-0
The main lines of the Closed Ruy Lopez continue 6.Re1 b5 7.Bb3 d6 8.c3 0-0. White can now play 9.d3 or 9.d4, but by far the most common move is 9.h3 which prepares d4 while preventing the awkward pin ...Bg4. This can be considered the main line of the opening as a whole and thousands of top-level games have reached this position. White aims to play d4 followed by Nbd2–f1–g3, which would firmly support e4 with the bishops on open diagonals and both knights threatening Black's kingside. Black will try to prevent this knight manoeuver by expanding on the queenside, taking action in the centre, or putting pressure on e4.
After 6.Re1 b5 7.Bb3 d6 8.c3 0-0, we have:
- 9.d3 (Pilnik Variation)
- 9.d4 Bg4 (Bogoljubow Variation)
- 9...Na5 (Chigorin Variation)
- 9...Bb7 (Zaitsev Variation)
- 9...Nb8 (Breyer Variation)
- 9...Nd7 (Karpov Variation)
- 9...Be6 (Kholmov Variation)
- 9...h6 (Smyslov Variation)
The Pilnik Variation, named for Herman Pilnik, is also known as the Teichmann Variation from the game