The Ushiro-goshi (Back hip throw) is classified as a counter Waza, and consists of grasping the opponent in a bear hug, lifting him, and throwing him down as if thrusting out one's stomach.
From the natural posture, the opponent attempts a Waza, pulling Tori forward with both hands while stepping toward Tori. The opponent then spins around to place his back against Tori, and, as he begins to draw Tori onto his hip, Tori counters with this Ushiro-goshi (Back hip throw) Waza.
First, Tori bends his knees to lower his body, positioning his knees in the hollows behind Uke (Player receiving opponent's attack) knees.
This knee positioning disables the spring force of Uke knee at the leg which intended to use as a fulcrum, and effectively ends his Waza attempt.
Tori then releases his Hiki-te (Pulling hand) grasp on Uke sleeve and wraps both arms around Uke waist in a bear-hug grasp. In this posture, he lowers his upper body and with locked knees, destabilizes Uke balance toward the back.
In the instant Uke stretches in an attempt to improve his posture, Tori thrusts out his stomach against the back of Uke hips and lifts him high into the air.
Then, while pulling with the hand grasping Uke waist, and pushing with the hand grasping Uke collar, Tori throws Uke as if rotating him. Tori throws Uke straight downward, using the momentum from the spring-back action of his bowed body.