Biggles becomes involved in the struggles of an Eastern European country, Maltovia, against their neighbours. Biggles and the team are called to make up the entire airforce of Maltovia. They are forced to face both the enemy in the air along with treachery on the ground.

goodreads summary

In the uneasy atmosphere of Europe between the two World Wars, Biggles, Algy and Ginger are persuaded to defend a small European country from an aggressive neighbour backed up by an unnamed Big Power.