What is the theme in The Thirty-Nine Steps by John Buchan?

National identity is another crucial theme to The Thirty-Nine Steps. Ostensibly, there is the plot by "German anarchists" to steal British intelligence, bound for France, in an effort to start a war between Germany and Britain and eventually between all nations of Europe. In this way, Hannay's struggles can be colored as a British patriot doing his duty to protect his country, but in other ways cultural and national identities are more muddied. Hannay is a displaced, expatriate Scot, newly arrived in London from Rhodesia, then a British colony in Africa.