This chapter examines siege surrender rituals and the obstinate defence of practicable breaches during the Napoleonic Wars, with a particular focus on French obstinacy in the Peninsular War, which triggered the British general storms of Ciudad Rodrigo, Badajoz and San Sebastian. Whereas a century earlier Louis XIV’s fortress governors had surrendered at the point of a practicable breach or beforehand, Napoleon’s now fought on. This chapter explores how this had come to pass, the extent to which eighteenth-century siege surrender conventions were disrupted during the Peninsular War and Napoleonic Wars more generally, and British attitudes and practices towards siege defences taken to the last extremity. On the one hand, French garrison commanders were adhering to Napoleon’s orders to defend practicable breaches, which became the subject of an instructional treatise by Lazare Carnot. On the other hand, this was the culmination of a much broader and long-term evolution in cultures of war and honour codes – that encouraged a cult of obstinacy. The chapter concludes by comparing siege surrender in Spain with siege defences and capitulation throughout other regional theatres of war and campaigns during the Napoleonic Wars.