The first book is written by Christine Denniston and it is presenting the tango at Golden Age. This posting is a short excerpt from sacada section in the book. She is happy to describe how complex the variety of movements was at that time and how these old moves are coming up as new ones today.
The word *sacar* means to take out or remove and in this context it can be seen as removing the partner's foot from a place you want to occupy. This class of steps is mostly an illusion where the reason for follower's movement is far above the floor. It is NOT caused by a kick on follower's leg but by the cooperation of the upper bodies.
One of the usual, easy steps to target a sacada to is the follower's right foot side step. The leader will extend his right leg forward to initiate the exchange of places. Sometimes even the follower's backward step was used while the leader did the sacada forward.
When we explore the side step sacada the process is initiated and completed during the weight transfer.
One of the basic rules for Golden Age leader was to keep the feet under or behind you; never let your foot pass forward beyond your chest. During the sacada you violate this rule and the foot is following the line to the followers heart and even passing it when your toes are landing behind the follower's back. With other words both the heart and foot are following the direction to follower's heart.
The leader is taking the follower's former place during a turning movement for both. The outcome of planeo or gancho is caused by the dynamics of the movement.
In this otherwise so clear description I am missing more detailed information about the turn, when follower's hips are moved away so the leader can take the space. You get some information about the timing in this Oscar Casas video with Mary Ann.
The preparing figure is an Americana giving a good start for her sidestep. They show us both a light and a deep sacada.
The sacada part starts about at 2.00
This is the starting position after she has turned around after an Americana. In the down left corner you find the exact time for this moment. Oscars right foot has passed behind the place of Mary Ann's heart.
Here you find the three phases of the turn.
Christine Denniston: the meaning of TANGO, The Story of the Argentinian Dance