Tukhachevsky used concentrated attacks to exploit the enemy's open flanks and threaten them with envelopment. Allied forces began an envelopment of the German forces remaining in Normandy. The tactic resulted in a double envelopment. HSV-1 undergoes a process of primary and secondary envelopment. Therefore, they can simulate reflected sound waves and improve subjective sense of space and envelopment. Enver's plan involved a single envelopment using three Corps. The Marines used the term vertical envelopment instead of air mobility or air assault. Emphasis on operational envelopment came from the knowledge of a likely tactical stalemate. While a successful tactic, there are risks involved with performing an envelopment. The Soviets planned Operation Uranus as a double envelopment. Greene's division helped prevent the envelopment of American forces and allowed for a safe retreat. He is regarded as a cosmic force for separation, despair and spiritual envelopment. Pleasonton's attack plan called for a double envelopment of the enemy. The Marines used the term "vertical envelopment" instead of "air mobility" or "air assault". Their capture would accelerate the envelopment of the German divisions near St. Mihiel.