411 REFERENCE · Wikibooks
Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nc6/3. Bc4/3...Bc5/4. c3/4...Nf6/5. d4/5...exd4/6. cxd4/6...Bb4/7. Nc3/7...Nxe4/8. O-O
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Greco’s Gambit
White castles her king. This unpins her knight to her king, causing the black knight on e4 to be hanging. Due to the open e-file creating complications should black retreat her knight, black generally exchanges on c3. While …Nxc3 is appealing to keep the bishop pair, it enters the rabbit hole.
Therefore, Black should play …Bxc3, where after exchanging, there is no hanging piece, giving her time to play …d5