During the 1810s and 1820, officials in the War Department engaged in military state building, which transcended partisanship and contributed to the development of executive autonomy. The process revealed the ability of the executive to shape national security, while also foreshadowing Progressive Era trends toward expertise-based bureaucratic autonomy. The activities of the Ordnance Department suggest that the connection between war and early American state building was forged in the efforts to bolster the armaments industry. Ordnance officers established autonomy partly through arms expertise, and they were not necessarily coalition builders like the late nineteenth-century Post Office and Department of Agriculture bureaucrats, especially because they generated more hostility. Thus, there were different routes by which autonomy was and is established, but in the first decades of the nineteenth century, this autonomy depended on national security and war preparations. This article uses War Department papers, armory records, and congressional debates to show how certain bureaucrats developed the ability to work against congressional limits to their functionality. Ordnance ultimately succeeded because its leaders executed a nonpartisan military agenda and demonstrated an ability to effectively manage the nation's security apparatus, especially in times of peace.