Inondations-Plan der Festung Theresienstadt

An exceedingly rare 19th-century ‘Inundation Plan’ of Theresienstadt Fortress.

This incredible, possibly one-of-a-kind engineering plan outlines the extensive defensive works of the Theresienstadt Fortress (now Terezín, in modern-day Czechia) complex at a pivotal moment near the end of the 19th century. Its strategic position at the confluence of the Eger and Elbe Rivers, on the approaches to Prague, led Habsburg Emperor Joseph II to order its construction in 1780. Extensive brick and earthwork walls, miles of subterranean tunnels, and separately defensible forts on either side of the Eger made Theresienstadt a formidable complex. However, the presumed Prussian invasion threat never materialized, and the fortress was never directly attacked.

The development of rifled artillery and explosive shells made its masonry defenses increasingly obsolete. As a result, Theresienstadt gradually transitioned from an active fortress into a garrison town and military prison. By 1882, it had been stricken from the list of “official” fortresses maintained by the Austro-Hungarian monarchy. However, there was one defensive element that would retain its utility well into the 20th century: the ability to flood the surrounding low-lying area using a carefully managed system of sluices, dikes, and channels.

That was the purpose of this Inundation Plan, originally drawn in 1876 by the Kaiserlich-Königliche (K.K.) Genie-Direction of Theresienstadt, the military engineering authority of the imperial Austrian Army. A meticulous outline of the Small and Large Fortresses showcases the concentric series of brick walls, ditches, and detached works that not only defended the interior but also integrated a complex hydraulic system. By releasing certain gates, the fort commandant could flood the surrounding low-lying areas—approximately 390 acres at maximum inundation. This would severely impede the movement of an attacking army, transforming roads and fields into waterlogged obstacles and making the approaches to the fortress considerably more difficult to traverse.

These “cauldrons” (Kessels), shaded in light blue, almost entirely cover the approaches to Theresienstadt from the north, east, and south. Scores of numerical annotations indicate elevation data, a critical element in determining the efficacy of the plan. The unprotected areas are covered by additional redoubts, highlighting the importance of the inundation system to the overall defensive strategy. In spite of the scientific nature of the engineering diagram, constant maintenance was required to ensure that the system worked as intended. An extensive text box, attributed to Leutnant F. Plejnar?, in the lower right outlines how the plan was revised in 1889, with the resulting recommendation that approximately 4.5 meters (over 15 feet) be added to the stated elevations.

In the decades following the creation of this plan, the history of Theresienstadt took a decidedly darker turn. The most famous prisoner held within its walls was Gavrilo Princip, the assassin of Archduke Franz Ferdinand, who died there of tuberculosis in April 1918. After the dissolution of Austria-Hungary following World War I, the new state of Czechoslovakia retained a military garrison at the site. Following the Munich Agreement of 1938 and Germany’s subsequent occupation of the Czech lands in March 1939, Terezín once again came under German military control.

Beginning in November 1941, the Nazis transformed the fortified town into the Theresienstadt ghetto, a transit and internment center for Jews from across German-occupied Europe. The fortress’s existing barracks, houses, and military infrastructure were repurposed to accommodate an enormous and rapidly growing prisoner population. More than 140,000 Jews passed through Theresienstadt between November 1941 and April 1945; approximately 34,000 died in the ghetto itself, while the vast majority of those deported onward were murdered elsewhere.

The Small Fortress, meanwhile, served as a Gestapo prison for political prisoners and others persecuted by the Nazi regime. Thus, the military landscape depicted on this 19th-century plan- its walls, barracks, ditches, gates, and carefully controlled approaches – was repurposed for an entirely different kind of confinement less than a century later.

Sources: UNESCO; EBSCO; IDNES; IROZHLAS