Produced shortly before the outbreak of World War II in September 1939, If War Should Come was one of the last films to be produced by the GPO Film Unit before it was re-named the Crown Film Unit and incorporated into the Films Division of the Ministry of Information.
Made for theatrical release, the film comprises a catalogue of civil defence precautions to be taken by householders in the event of war. The soothing Elgar soundtrack over commentator Jack Livesey's instructions to keep "buckets of water and sand ready on the landing", "a pencil and paper by the wireless set" and "your gas mask handy" were designed to instil calm and reassurance at a time of uncertainty. However, the instruction not to be alarmed by the sample blasts of air- raid sirens might have been asking too much of an anxious cinema audience for whom such noises weren't yet commonplace.
Despite its matter-of-fact approach, for today's audience the film has a special poignancy borne of knowledge of the reality that lay ahead. Just a month later, the original project had been overtaken by events and the film was hastily revised and awarded the more urgent title Do It Now in time for release at the outbreak of war. It was shown in 2,000 cinemas throughout the country in the week beginning 18 September 1939. Simultaneously, the accompanying leaflet campaign 'Some Things You Need to Know if War Should Come', issued by the Lord Privy Seal's Office in July, was redrafted for mass dissemination when war became a reality rather than an expectation.