Fort Heldsberg was built 1938–1940 near St. Margrethen in Switzerland, overlooking the Rhine, which forms the Swiss-Austrian border at that location, just south of Lake Constance.

The fort at Heldsberg was planned to stop or delay an attack across the nearby Rhine, as well as providing artillery coverage on the southern end of Lake Constance.

[1] The German plan for a Swiss invasion, Operation Tannenbaum, noted the presence of the Heldsberg position and concluded: A very desirable approach is to attack from the east at Rheineck, the shortest way to the enemy flank, but the mountainous terrain and the strong fortifications at Rheineck (Heldsberg) promise no success.

[4] The surface components, running roughly from west to east, include: The fort commands the rail crossing of the Rhine.

[5] A number of unconnected satellite bunkers support the main fort and provide covering fire for anti-tank barriers.