The Réti Opening Proper arises after 1.Nf3 d5 2.c4. ECO code: A09.

Overview

This is the Réti Opening in its strictest definition—White develops the knight and immediately challenges Black's central d5-pawn from the flank with c4. The position is the starting point for one of the richest complexes in hypermodern opening theory.

Main Lines

Black's three main approaches are:

• 2...e6 – Holding d5, often transposing into the Queen\'s Gambit Declined after 3.d4.

• 2...c6 – The Slav approach, also holding d5; 3.d4 transposes into the Slav Defence.

• 2...dxc4 – The Réti Accepted, giving up the centre. White can regain with 3.e3, 3.e4, 3.Na3, or 3.Qa4+.

• 2...d4 – The Advance Variation, gaining space but potentially overextending. White responds with 3.e3 or the gambit 3.b4.

Strategic Themes & Plans

White aims to control the centre hypermodernly with Bg2, 0-0, and central pawn breaks (d3–e4 or d4). The Réti's great strength is its transpositional flexibility—White can steer toward the Queen\'s Gambit, Catalan Opening, or English Opening depending on Black's response. This flexibility makes it a favourite of top-level players who wish to avoid opponents' specific preparation.