Although this seems like a simple background detail, or merely a way to setup the climax in the story, his dissatisfaction with English life frames the overarching theme of the novel: English nationalism. Like many other fictional works from Great Britain in the spy or war genres, The Thirty-nine Steps has a nationalistic theme. Within this larger theme is the sub-theme of defending English soil and sovereignty.

The root of this theme's recurrence in the genre is the actual experiences of English people during World War I and World War II. There is a hint of mass trauma among the British people, and this is evident in the countless period films, television series, and fictional work containing such themes. The Thirty-nine Steps was published during Great Britain's involvement in World War I and at a time when paranoia over espionage plagued the country.

Another theme, which is not as evident, is the UK's tense relationships with the rest of Europe. The British Isles has had a tumultuous relationship with continental Europe since the beginning of ancient British civilization, and it continues to this day (e.g., Brexit).