Rules question | Golf Monthly

Rule 13-2 states that there is no penalty if the action occurs in making a stroke or the backward movement of a club for a stroke and the stroke is made. If you discontinue the stroke therefore no stroke is made and so a penalty may apply. This is clarified in Decision 13-2/14.5 Branch Broken on Backswing and Swing Discontinued which says

Q. A player’s ball lies under a tree. The player fairly takes his stance and starts his backswing with the intention of making a stroke. Near the top of his backswing his club strikes a branch and breaks it. At that point he discontinues his swing. Rule 13-2 states in part: “… a player must not improve … the area of his intended stance or swing …except … in making a stroke or the backward movement of his club for a stroke.” Is the player exempt from penalty under this exception?

A. No, because the swing was discontinued the backward movement of the club was not in fact the backward movement for a stroke."