This work suggests that Humphrey Jennings' re-enacted documentary about the London Blitz, "Fires Were Started" is an understated propaganda masterpiece whose documentary value, despite the reconstructions required by film technology in the 1940s, remains undimmed. The author provides a full account of exactly how Jennings recaptured the reality of the Blitz for his cumbersome camera through a process of meticulous research and extraordinary sensitivity.