By now, when he was twenty-five, the little stratagem may well have been mostly reflexive, just as a veteran baseball player, at the plate, will tap his spikes with his bat whether he needs to or not.
There are no more uses of "stratagem" in the book.
Show samples from other sources
And I think of rats again and how sometimes, to pass the interminable hours, Teacup and I would plot our campaign against the vermin, stratagems and tactics, waves of attack, each more ridiculous than the last, until she dissolved into hysterical laughter, and I gave her the same speech I gave Zombie on the firing range, the same lesson that now comes home to me, the fear that binds killer to prey and the bullet connecting both as if by a silver cord.
Rick Yancey -- The Infinite Sea
If more is said that Marie-Laure cannot overhear—if there is a pantomime going on between them, notes passed, stratagems agreed upon—she cannot say.