What is nbd2

lol that last one surprised me, I didn't know there was a convention where you had to specify both the file and the rank of your piece. Perhaps the Russians didn't want to bother with that stuff because I believe what they did back in the day was just write down the original square and the new square of the piece they moved, with the only necessary exception being promotion of a pawn.

lol that last one surprised me, I didn't know there was a convention where you had to specify both the file and the rank of your piece. Perhaps the Russians didn't want to bother with that stuff because I believe what they did back in the day was just write down the original square and the new square of the piece they moved, with the only necessary exception being promotion of a pawn.
You don't. It was needed for a not realistic example of 4 knights. Normally the 2 pieces would be on different ranks or different files (otherwise they would be on the same square!)
I guess that if there is only one Queen coming from the f-file (in this situation), the notation would go as usual instead of the letter-number format. The letter-number format is just there to avoid possible ambiguities. In over-the-board notation recording, though, I sometimes overlook/miss these notations by just writing Nd2 instead of Nbd2 at times.
Two or more knights can go to d2, but the knight on the b file goes to d2.