Vendade riigisaladus : Soome ja Eesti salajane sõjaline koostöö Nõukogude Liidu võimaliku rünnaku vastu aastatel 1918-1940

Between the World Wars, Estonia and Finland developed extensive but highly secret military cooperation aimed at defending against a potential Soviet attack, including joint naval planning and coordinated coastal defense operations in the Gulf of Finland. After World War II, this collaboration became a taboo subject due to Soviet occupation of Estonia and political sensitivities in Finland, leading to decades of silence about the partnership.