First a little history on the QG opening, it’s one of the oldest known openings having been mentioned as far back as 1490 and anaylized throughout the 17th by Greco and 18th by Stamma. In early modern chess Queen pawn openings were not as common as King pawn, this was during the swash buckling and heroic Romantic Era on the board where grand Checkmates were the fashion. Opening with 1.d4 led to slower more positional games which hadn’t been picked up until the tournament in Vienna in 1873.
Here is our starting point for the QGD:Marshall as I will always capture the central pawn with the wing pawn. After cxd5 Black is forced to recapture with the Queen or the Knight if Black recaptures at all. Although I have never seen anyone play 3…c6 which leads to the Tan Gambit, it is a choice of response however the majority of the people will recapture. Rare as other variations may be I will still take a look at them in the analysis linked below along with the mainlines and personal preferences and why.