As Europe approached the brink of war, international exhibitions increasingly narrowed their focus to specialized themes with direct relevance to modern life. Infrastructure, resources and applied science replaced broad encyclopedic surveys, reflecting both technological priorities and geopolitical uncertainty.

Liège assumed this role in 1939. Officially titled “Exposition internationale de l’eau,” Expo 1939 Liège was held from May 20 to October 29, 1939, in Liège, Kingdom of Belgium. The event is recognized by the International Exhibitions Bureau (Bureau International des Expositions, BIE) as a Specialised Exhibition, dedicated to the theme of water and its role in modern society.

Organized in the final months before the outbreak of World War II, the exposition addressed water as a critical resource for public health, industry, transportation and urban development. Its thematic clarity distinguished it from earlier general-purpose Expos and aligned it with the evolving model of focused, problem-oriented exhibitions.

The exhibition was primarily located in the Parc de la Boverie, along the banks of the Meuse River. This setting reinforced the exposition’s subject matter, allowing water to function simultaneously as theme, exhibit and landscape element. Pavilions, promenades, and demonstration zones were arranged to integrate natural and engineered waterways into the visitor experience.

Architecture combined temporary exhibition structures with existing buildings adapted for the event. Displays emphasized hydraulic engineering, drinking water systems, sanitation, flood control, inland navigation and hydroelectric power. Scientific and technical exhibits explained water management through models, diagrams and operational demonstrations, translating complex infrastructure into accessible public narratives.

International participation included contributions from multiple countries, particularly European nations with advanced experience in water engineering and river management. National and institutional exhibits presented comparative approaches to irrigation, port construction, water purification and maritime transport, framing water as both a shared challenge and a field of international expertise.

Public engagement during the 1939 season was strong, though inevitably shaped by the tense political climate. The exposition opened only months before the German invasion of Poland in September 1939, and growing uncertainty affected travel and international exchange toward the end of its run. Despite these constraints, the event succeeded in presenting water as a foundational element of modern civilization.

Expo 1939 Liège occupies a distinctive place within the Expo tradition. As one of the last international exhibitions held in Europe before the outbreak of global war, it illustrates the late interwar shift toward specialized themes grounded in infrastructure and public welfare. Its focus on water anticipated postwar priorities in reconstruction, environmental management and urban resilience.

Although plans existed to extend or revive the exposition in 1940, the escalation of World War II brought international exhibition activity in Europe to an abrupt halt. In retrospect, Expo 1939 Liège stands as a closing chapter of the interwar exhibition era, marking the transition from peacetime exchange to wartime rupture.