"All warfare is based on deception. Hence, when we are able to attack, we must seem unable; when using our forces, we must appear inactive; when we are near, we must make the enemy believe we are far away; when far away, we must make him believe we are near."
― Sun Tzu, The Art of War
Deception as applied in sports in general and badminton specifically is critical especially at advanced skill levels. The opposite of Deception is Anticipation . A skilled player would try to gain advantage by anticipating the opponents next shot. On another hand, knowing that the opponent is also trying to read one’s own movements as the shot is being made, deception is used to misdirect the opponent.
Note that deception does not necessarily need to win the point outright. Deception has 3 major Advantages
1) Aerobic: Opponent needs to work harder to recover from the misdirection. This wears down the opponent over the course of the match. E.g. deceiving the opponent on a perceived net shot only to flick the shuttle to the backline forces the opponent to expend a lot of energy to change direction and recover to the backline.
2) Gaining the initiative: Opponent usually returns with less quality as the shuttle is hit late. The next shot from you is to pull the opponent yet wider, till the advantage is clear cut for a winning shot. E.g. a cross court drop pulls the opponent to hit a 3/4 deep shot to the backline. Instead of an outright smash, you can hit a low, fast clear to the opponent’s backhand forcing a yet weaker shot and you can kill the shot with a smash.
3) Regaining the initiative: If you have been deceived by your opponent and he/she expects a certain shot as you respond, you can deceive the opponent with a shot that your opponent does not expect and regain the initiative.
When to apply Deception:
You should use deception selectively. Lull your opponent into “reading” your style and execute the deception when it matters. If you use your deception too often, your opponent will switch to watching the shuttle after it is hit and not anticipate as much.
Note that for every badminton stroke that you make, the anticipated shot and the deceptive shot must be made with the same motion and pace. That motion and pace must be fast on all shots - that is a prerequisite. If your normal shot is not there yet, practice that first (this could take a while, don't skip this step). If your motion and pace is slow, the opponent will not feel threatened to anticipate as much and your attempted deception will be for naught.
To understand Deception, it requires you to be an astute study of the full body motion, head, arm, and racket head angle of every badminton shot. Try out the fluid, expected motion in front of a mirror to learn what are the subtleties that telegraph what the shot will be (or rather, supposed to be). Once you have mastered that, add another dimension to it - the position on the court where the stroke is made. Very often, depending to where you are on the court, certain shots are “standard”.
Next, with exactly the same beginning motion, try the last 20–30% of the completion motion to do another shot. You can vary racket motion in single sweep or with double motion or even triple motion. Note that full motion to racket motion needs to be subtle to complete of the shot. Otherwise, there would be no deception and you will most likely throw off your own rhythm and make an error.
You want to keep the opponent unbalanced and on the “back of their feet” at all times. In the modern era, I suggest you study the masters of deception - Tai Tzu Ying and Peter Gade on youtube (over and over again), pick one shot and practice (a lot) to refine on the anticipated shot and deceptive shot. Vary the angles while keeping the pace and motion the same. Move to the next shot and so on. Put the shots together in a practice session. Also, practice mentally by visualisation of your full body motion as you hit the shots. Then apply in a real game - be brave and have fun!