Dig For Victory was a film encouraging people to grow their own vegetables in 1942. The film was created by re-using footage from earlier films along with some new scenes. Another version of this film was made to be shown in the USSR, one of Britain's allies in the war.
The film is easy to understand if you know what was happening at the time it was made. By 1942 the USA had joined the war against Germany. This changed the balance of power in the war. However, at the time this film went out it was certainly not clear that Germany would be defeated.
German submarines were attacking ships supplying Britain with food, weapons and equipment from Canada and the USA. This campaign was known as the Battle of the Atlantic. British Prime Minister Winston Churchill claimed that the possibility of losing the Battle of the Atlantic was the only thing which ever frightened him during the war. This was one reason why the film was made. If people grew more food in Britain, then they would not need to import as much food. This in turn would mean that ships could bring in more of other vital supplies to help win the war.