Form III focused on strong defensive technique to essentially outlast an opponent, waiting until he began making mistakes due to frustration or fatigue, before taking advantage of these lapses and countering. A master of Soresu was considered invincible, and the focus on long-term survival allowed such duelists to take stock of and control of their situation, choosing to kill, disarm, or even reason with enemies.
E ele não só o usou, ele o dominou :
Even masters such as Mace Windu acknowledged Kenobi’s prowess with this form; indeed Windu once claimed that Kenobi was not a master of Soresu but the master of Soresu.
Isso é exatamente o que aconteceu no duelo no Mustafar . Kenobi estava tentando argumentar com seu velho amigo. Ele usou o terreno para se colocar em uma situação em que poderia negociar com ele, mas Vader estava zangado demais para sequer pensar nisso. Tudo o que ele queria era matá-lo e mostrar-lhe a extensão e a superioridade de seus novos poderes. Ele ameaçou a vida de Kenobi com seu último movimento, então Obi-Wan escolheu usar esse erro para desarmá-lo completamente:
Perched on a rise above the lava river, Kenobi warned Vader not to attack, but the Sith Lord ignored him, blinded by arrogance and rage. As Vader leapt at Kenobi, blade angled for the kill, he left himself open, allowing Kenobi to execute a vicious Mou kei finishing move, dismembering Vader with one swift strike. Vader’s left arm and both of his legs were severed. Dropping his lightsaber, Vader rolled to the brink of the lava river.