In April 1941, the Royal Navy and the RAF devised Operation Fuller, a plan for combined operations against the ships in Brest should they sortie.
The RAF alerted its forces involved in Operation Fuller to indefinite readiness and on 3 February, 19 Group, Coastal Command began night reconnaissance patrols by Air to Surface Vessel Mk II (ASV) equipped Lockheed Hudsons, supposedly able to detect ships at range.