This report explores the development of Rostec State Corporation, Russia's largest defence-industrial conglomerate, and the challenges it faces in connection with Russia's war against Ukraine. Rostec's founding in 2007 marked the culmination of the state's reassertion of control over the Russian defence industry during the 2000s, driven by the perceived need for oversight of a strategic industry. Its configuration as a "state corporation" subordinated to the Russian president has also shielded Rostec from competing interests in a political system with weak formal protections. Rostec has more than doubled in size and revenues since then, acquiring a monopoly over several major weapons platforms. Rostec has continued to grow since Russia's full-scale invasion of Ukraine in 2022. Yet the corporation's efforts to increase production have encountered constraints. Consequently, the Russian government has supported the defence industry with subsidies and concessional loans. This development has exposed tensions between the political system and the leadership's wartime materiel needs. Going forward, the constraining factor on Rostec's output will not be the financial sustainability of its enterprises, but rather the state's fiscal capacity, labour supply, access to foreign inputs, and availability of existing equipment stocks. The West's sanctions policy and military support for Ukraine play a key role in this context.