The most popular second move for White is 2.Nf3, attacking Black's pawn and supporting the pawn advance d2–d4. The Open Games include many of the oldest and most deeply analyzed openings in chess. They are often among the first openings taught to beginners and remain frequently played at all levels.
Two of the most analyzed of the Open Games are the Ruy Lopez (1.e4 e5 2.Nf3 Nc6 3.Bb5) and the Italian Game (1.e4 e5 2.Nf3 Nc6 3.Bc4). Also popular are the Scotch Game (1.e4 e5 2.Nf3 Nc6 3.d4) and the Petrov Defense (1.e4 e5 2.Nf3 Nf6).
When written in lowercase, the term "open game" can be used to refer to "open" chess positions, which feature open lines, meaning unobstructed files and diagonals; these increase piece mobility and often lead to tactical gameplay. While 1.e4 e5 tends to lead to open positions, this is not always the case.
Other responses to 1.e4 are termed Semi-Open Games.
White's most popular first move, 1.e4, moving the king pawn two squares, immediately stakes a claim in the center and frees two pieces (the queen and king's bishop) for development. Bobby Fischer called 1.e4 "Best by test." On the negative side, 1.e4 places a pawn on an undefended square and weakens the squares d4 and f4 (White can no longer play e3). The symmetrical 1...e5 incurs similar strengths and drawbacks for Black.
White's response 2.Nf3 attacks Black's undefended king pawn, prepares to castlekingside, and supports playing d2–d4 in many lines. Black typically defends the pawn with 2...Nc6. The counterattack 2...Nf6 is also common and sound. Defending with 2...d6 is also seen, but 2...f6 is unsound.
1...e5 was the most common response to 1.e4 for centuries, though sometime in the mid-20th century the unbalancing move 1...c5, the Sicilian Defense, became slightly more popular among tournament players.
Black's usual reply to 2.Nf3 is 2...Nc6, defending the king's pawn from White's knight and developing Black's own knight. From here, several named openings can arise:
3.Bb5, the Ruy Lopez, also known as the Spanish Game or Spanish Opening, is White's most frequent move at the top level, and one of the most extensively played and analyzed openings at all levels of chess. Black's most common response is 3...a6, forcing White to make a decision between exchanging the bishop for the knight with 4.Bxc6 or retreating with 4.Ba4. Also common is 3...Nf6, the Berlin Defense. Black has several alternatives, the sharpest of which is 3...f5, the Jaenisch Gambit (or Schliemann Defense).
3.Bc4, the Italian Game, is White's second most popular move, and has been extensively analyzed for hundreds of years. It usually leads to either the Giuoco Piano (3...Bc5) or the Two Knights Defense (3...Nf6), where White may play 4.Ng5, 4.d4, or 4.d3. In the Giuoco Piano, White can play 4.c3 and 5.d4, the classical approach; 4.b4, a sharp pawn sacrifice known as the Evans Gambit; or 4.c3 and 5.d3 (also reached with other move orders), the modern approach, among various other plans.
3.d4, the Scotch Game, was popular in the 19th century and is still the third most common move. After the usual 3...exd4, White may either recapture with 4.Nxd4 with an approximately equal game, or play the Scotch Gambit (4.Bc4), a risky but dangerous tactical line against an unprepared opponent.
3.Nc3, the Three Knights Game, was also a popular move in the 19th century and is still occasionally played at the top level. Black's usual reply is 3...Nf6, the Four Knights Game. It frequently leads to positional games and is generally considered less challenging for Black to defend against than the three lines above.
3.c3, the Ponziani Opening, has never achieved widespread popularity but is occasionally used as a surprise weapon.
After 2.Nf3, there are two main alternatives to 2...Nc6:
2...Nf6, the Petrov Defense, a popular choice at the top level. It has a drawish reputation but there are many sharp lines. After 3.Nxe5, Black should reply 3...d6 4.Nf3 Nxe4; the natural looking 3..Nxe4?! is insufficient for equality after 4.Qe2. Besides 3.Nxe5, White may also play 3.d4. Alternatively, White can avoid the extensive theory of the Petrov with 3.Nc3, which often transposes into a Four Knights Game with 3...Nc6.
2...d6, the Philidor Defense, defends the pawn on e5 but has the disadvantage of restricting the mobility of Black's king's bishop, and typically leads to solid but passive positions for Black. For this reason, it largely fell out of favor by the early 20th century as Black players sought more dynamic options, but it has a dependable reputation.
The following moves are rare and generally considered dubious:
2.f4, the King's Gambit, where White offers a pawn to undermine Black's center and achieve quick development. It was very popular before the 20th century with master and amateur alike. Black often accepts the pawn by playing 2...exf4, but there are alternatives, such as 2...d5, the Falkbeer Countergambit, which counterattacks in the center.
2.Nc3, the Vienna Game, which became popular for a while in the 19th century, also frequently features such attacks on Black's center by means of f2–f4, but there are multiple alternative plans, such as 3.Bc4, developing the bishop to an active square, and 3.g3, intending to fianchetto with Bg2.
2.Bc4, the Bishop's Opening, was also more popular in the past. It often transposes to the Italian Game or Vienna Game, but there are several independent lines.
2.d4 is the Center Game, in which White immediately opens up the center. After the recapture 2...exd4 3.Qxd4, Black gains a tempo by attacking White's queen with 3...Nc6. An alternative is to sacrifice one or two pawns by offering the Danish Gambit (3.c3); however, a safe practical reply for Black is to decline the gambit with 3...d5.
Other second moves are rare and do not gain any advantage against correct play:
2.Qh5, the Danvers Opening, also known as the Parham Attack or Wayward Queen Attack, is usually played only by amateurs, though Hikaru Nakamura has experimented with it in grandmaster tournaments.
2.Qf3, the Napoleon Opening, has even less to recommend it as Black can easily block any mating threats without compromising development.
2.Bb5, the Portuguese Opening, rarely played and well met by 2...c6 or 2...Nf6.
Emms, John; Flear, Glenn; Greet, Andrew (2008). Dangerous Weapons: 1 e4 e5: Dazzle Your Opponents in the Open Games!. London: Everyman Chess. ISBN9781857445428.
Bologan, Victor (October 2014). Bologan's black weapons in the open games: how to play for a win If white avoids the Ruy Lopez. Alkmaar, The Netherlands. ISBN9789056915438. OCLC878505291.{{cite book}}: CS1 maint: location missing publisher (link)
Davies, Nigel, 1960- (2005). Play 1e4 e5!: a complete repertoire for Black in the open game. London: Everyman Chess. ISBN1857444019. OCLC71338396.{{cite book}}: CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link)
Emms, John. (2000). Play the open games as Black: what to do when White avoids the Ruy Lopez. London: Gambit. ISBN1901983277. OCLC45466779.
Lokander, Martin (7 January 2016). Opening repertoire: the open games with black. London. ISBN9781781941942. OCLC922562228.{{cite book}}: CS1 maint: location missing publisher (link)
