Let the enemy think they don’t have to work so hard to defeat you. If Sun Tzu didn’t write something like that, he should have.
Energy:
17. Simulated disorder postulates perfect discipline, simulated fear postulates courage; simulated weakness postulates strength.
18. Hiding order beneath the cloak of disorder is simply a question of subdivision; concealing courage under a show of timidity presupposes a fund of latent energy; masking strength with weakness is to be effected by tactical dispositions.
Yes he did.
"Pretend inferiority and encourage his arrogance." Sun Tzu