In 1936, the 7th Battalion was converted into 39th (The Lancashire Fusiliers) Anti-Aircraft Battalion, Royal Engineers, based in Salford. After mobilising in August 1939 to defend potential targets such as the Manchester Ship Canal and Barton Power Station during the Phoney War, it served in the Orkneys, guarding the Scapa Flow naval base. It returned to Lancashire in early 1941 to defend Liverpool during the May Blitz. In the summer of 1940, while serving in 53 Anti-Aircraft Brigade, covering the North Midlands, it was transferred as a Searchlight Regiment to the Royal Artillery (the day of the actual transfer, 1 August (Minden Day), was considered auspicious by the battalion). In May 1943, the regiment was reduced to a cadre under its old title of 7th Bn LF and took no further part in the war, but several of its batteries continued an independent existence, continuing to wear the Lancashire Fusiliers badge and to celebrate Minden Day. 354th and 357th Searchlight Batteries (the latter converted into 414th Light Anti-Aircraft Battery) defended Southern England against V-1 flying bomb attacks in the summer of 1944 ('Operation Diver'). 356th Searchlight Battery took part in D-Day and was later converted into a 'Moonlight Battery' to provide 'movement light' or 'Monty's moonlight' to assist 21st Army Group's night operations during the campaign in .