Contemporary analysis of Egyptian emergency legislation and the military courts system typically reaches back only as far as the beginning of Mubarak era or the Free Officers’ courts of treason and revolution of 1952-53. Employing legal and news media and parliamentary, diplomatic and court documents from Egyptian, British and American archives, this paper will argue that the Egyptian government’s first long-term, autonomous administration of an exceptional legal system under the state of siege of 1 September 1939 to 4 October 1945 represented a significant expansion of the state’s political and social security objectives and triggered a wide-ranging renegotiation of local power with the British. It therefore set important precedents for governmental and legal strategy, social and economic goals and the role of security in nationalist discourse in the republican era. The state of siege, required by the 1936 Anglo-Egyptian Treaty in case of war, gave six successive Egyptian prime ministers power as military governors to issue more than 600 proclamations defining myriad new security regulations and infractions and placing many existing crimes under the jurisdiction of military-civilian mixed tribunals in which defendants had the right neither to habeas corpus nor to appeal. At first contented with war legislation imposing cooperative censorship and interning Axis citizens, the British authorities were forced to concede expanded Egyptian state economic control to areas formerly dominated by private foreign firms, and for the first time ever, Egyptian jurisdiction over British citizens in infractions of military proclamations. Parliamentary debate and military court records from the Egyptian National Archives illustrate a stark discrepancy between the objectives of war legislation and reality. Corruption in the new war bureaucracy and scant resources for the expanded police led to frequent failures in air raid defense and rationing and in preventing war profiteering, drug smuggling, theft and rioting between troops and Egyptians. Despite this, the crisis of war allowed the Egyptian government to reframe the issue of domestic security as a reserve of its nation-state and even redefine and nationalize aspects of time and space. This paper therefore elaborates a theory of emergency law in a neocolonial context: the state of siege became a subversive declaration of sovereignty that challenged British hegemony in the Egyptian security system. As it was based on liberal-legal discourse, it would have lasting consequences for state-society relations after the war.