Chess Opening Theory/1. e4/1...e5/2. Nf3/2...d6

Overview
The Philidor Defense (also referred to as Philidor's Defence) is a King’s Pawn Opening, primarily characterized by the move order 1. e4 e5 2. Nf3 d6. This defence arises in response to the king's pawn opening by White, and Black's subsequent reply signifies the Philidor's Defence. The main idea behind this defence for Black is to safeguard the pawn on e5 by placing pawns on both e5 and d6 squares.

Move Order
To reach the Philidor Defence, the game generally follows this sequence:


 * 1) White advances the King’s pawn two squares (1.e4).
 * 2) Black reciprocates by moving his King’s pawn two squares (1...e5).
 * 3) White, looking to pressure the e5-pawn, moves the knight to f3 (2. Nf3).
 * 4) Black counters by advancing the d-pawn one square, thus defending his e5-pawn (2…d6).

Historical Context
The roots of the Philidor Defense can be traced back to the 16th century. However, François-André Danican Philidor, an influential 18th-century French chess maestro, popularized it. Philidor's 1749 seminal work, "Analyse du jeu des Échecs", underscored the paramount importance of pawn structure, a breakthrough idea that significantly impacted chess theory. Within his treatise, he promoted 2...d6 as a robust retort to 1. e4 e5 2. Nf3, leading to the defence being indelibly linked with his name.

An iconic game that featured the Philidor was "The Opera Game" from 1858, played between chess prodigy Paul Morphy and two esteemed amateurs, Duke Karl of Brunswick and Count Isouard. They diverged from the standard lines with 3.d4 Bg4.

Though it enjoyed immense popularity in its early days, the Philidor's Defence' allure waned as positional play matured. By the onset of World War I, it had virtually disappeared from elite chess tournaments. In contemporary times, its usage in top-tier chess has been sporadic. However, there has been a slight uptick in its adoption in master-level play over the last two decades, especially in rapid and blitz formats.

Notwithstanding its historical significance, the Philidor Defense doesn't enjoy the same favour in contemporary top-level chess as other defences stemming from 1.e4 e5, such as the Ruy-Lopez or the Italian Game. Nonetheless, some elite players have wielded it occasionally as an element of surprise. It's worth noting that the ebb and flow of chess theory mean openings can oscillate in popularity, so it's plausible that newer top-tier players might be inclined to embrace the Philidor more consistently.

A few top players who have occasionally employed the Philidor Defense with the black pieces:


 * 1) Alexander Morozevich: Known for his unconventional opening choices, Morozevich has occasionally played the Philidor Defense and contributed to its modern theory.
 * 2) Radosław Wojtaszek: A top Polish grandmaster, Wojtaszek has played the Philidor in some of his     games.
 * 3) Wesley So: While not a frequent choice for him, So has occasionally tried the Philidor, especially in rapid and blitz games.

White's Strategy

 * 1) Central Dominance: By placing pawns on d4 and e4, White targets the center. The move d2-d4 is a logical approach that helps in expanding control.
 * 2) Piece Development: White generally moves the queen's knight to c3 and positions the king's bishop on c4 or e2.
 * 3) Apply Pressure: Using its central pawn structure, White pressures Black, targeting vulnerable points and preparing for possible Black pawn breaks like ...f5.
 * 4) * Key Moves:
 * 5) ** 3. d4: This is likely the best move. White can threaten a queen exchange with dxe5 dxe5 Qxd8+ Kxd8, preventing Black from castling. This move intensifies the pressure on the center, and the Black fortress might fall at any moment. White frequently seizes the chance to make the valuable d4 move in this setup.
 * 6) ** 3. Bc4: This move leads to a more positional game, which both sides can capitalize on.

Black's Strategy

 * 1) Instead of the typical knight to c6 move, Black defends the e5 pawn with a pawn. This distinctive method has both pros and cons. The Philidor Defence is a complex opening, with Black navigating many traps based on attacks on the f7 square. The defence's main advantage is that it complicates White's launch of an early attack due to Black's minimal weaknesses.
 * 2) * Key Points:
 * 3) ** By using the d6 pawn to support e5, Black spares other pieces (minor or major) from having to do so.
 * 4) ** This style of defence offers fewer vulnerabilities for Black.
 * 5) ** However, this also confines Black's own bishop on f8 and agrees to a more restrictive board position.
 * 6) Solid Foundation: The ...d6 pawn move furnishes a sturdy foundation for counterplay without immediately confronting White's central e4 pawn.
 * 7) Development Plans: Black can select from a range of development schemes. This could be preparing to fianchetto the kingside bishop with ...g6 and ...Bg7, observed in the Lion variation, or choosing ...Nd7 followed by ...Be7.
 * 8) Counterplay in the Center: Black regularly employs pawn breaks, primarily...f5 and ...d5, to challenge and counter White's central pawns.
 * 9) * Critical Perspective: If White dawdles in attacking, Black might play 3...f5 in response to a passive move from White, which could establish equilibrium. In the Philidor's defence, by defending the e5 pawn with another pawn, Black sidesteps some complications linked with the move, knight to c6, and subsequent moves like bishop b5 leading to the Ruy Lopez. Yet, the d6 move does concede some developmental potential, particularly concerning the f8 bishop.

Theory table
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'''1. e4 e5 2. Nf3 d6'''