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What is the Blackmar–Diemer Gambit?
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The Blackmar–Diemer Gambit is a chess opening in the Queen's Gambit Declined. White can use 5. g4 as a gambit option by continuing with 6. h4!?, which leads to sharp play and approximately equal chances. The push with 4... e3 is often used by strong players to avoid the complications arising from 4... exf3 5. Nxf3, but it is one of Black's weaker options against the Blackmar–Diemer as