Chess Opening Theory/1. e4/1...Nf6/2. e5/2...Nd5/3. d4/3...d6/4. c4/4...Nb6/5. exd6

= Alekhine Defence:Exchange variation = Black must decide whether he will take back with the c pawn : /5...cxd6/ or with the e pawn : /5...exd6/.

In the first case, Black will have a majority of pawns in the center, which may be useful for a later e5 push.

In the second case, the game will be more positional, relying more on the pieces placements than on the pawns fight.

Theory table
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'1.e4 Nf6 2.e5 Nd5 3.d4 d6 4.c4 Nb6 5.exd6'