Input (grade 13): It was built as the backbone of the regional fortification system, Festung Koblenz, by Prussia between 1817 and 1832 and guarded the middle Rhine region, an area that had been invaded by French troops repeatedly before.
Output (grade 9): It was built as part of the "Festung Koblenz" (Fortress Koblenz), by Prussia between 1817 and 1832 and guarded the middle Rhine region.