The world’s militaries account for up to 5.5% of total global greenhouse emissions, yet there is still no requirement for governments to report these emissions in international climate agreements. Researchers are therefore left on their own to assess military emissions. This may seem like an incredibly daunting task. The lack of data is even more stark during periods of conflict, where reporting is relatively non-existent. This article sets out a novel framework for examining greenhouse gas emissions from military supply chains including situations where emissions data are difficult to acquire due to supply chain complexity, or when data are purposefully held back under the guise of national security. We provide an empirical study of supply chain-based carbon from the US military’s use of concrete during the Second Iraq War (2003-08) to demonstrate its practicability. Concrete has a massive carbon footprint, and the US military uses a lot of it for protective walls, checkpoints, bases and bunkers. This work provides the tools to measure carbon embodied in military supply chains reinforcing recent calls for standardised frameworks emphasising the accounting of military environmental infrastructure footprints.