411 REFERENCE · Wikibooks
Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Bb4/3. Nxe5/3...Qe7
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not chess opening theory
3...Qe2! — Radium Gambit Accepted: Main Line
3...Qe2! immediately attacks the knight on e5 and creates a direct threat to regain the sacrificed pawn. Black uses the queen actively instead of developing another piece first.
4. Nf3 retreats the knight to safety and allows White to continue developing.
4. Nd3 retreats the knight to safety and it attacks the bishop t.
4. Nc4 keeps the knight active and maintains pressure on Black's position.
4. f4 supports the center and gives more space while the knight remains under pressure.
4.a3 attacks the bishop while the knight is hanging.
Downsides: Black's queen is developed very early and can potentially be exposed to attacks by White's developing pieces. White can use the tempo gained from attacking the queen later to catch up in development.
The Radium Gambit Accepted: Main Line is characterized by 1. e4 e5 2. Nf3 Bb4 3. Nxe5 Qe2!, with Black immediately using the queen to challenge White's knight and fight for the sacrificed pawn.