Academy | Calculation | Counting | Example #3
We could calculate all the captures after 1. d4:
1. d4 exd4 2. exd4 Bxd4 3. Nxd4 and now we notice Black cannot play 3… Nxd4 because the knight on c6 is pinned by the White queen.
Alternatively, instead of calculating all those moves, we could simply count: White has three defenders on d4 (pawn, knight, queen), and Black has three attackers (pawn, bishop, knight). Since the number of attackers and defenders on the d4-square is equal, White would capture last in a series of trades.
In fact, the knight on c6 is pinned, so Black effectively has only two attackers on the d4-square. Therefore, playing 1. d4 is likely safe, though we should still double-check to be sure.