It was built as the backbone of the regional fortification system , LOCATION@1 , by LOCATION@2 between NUMBER@1 and NUMBER@2 and guarded the middle LOCATION@3 region , an area that had been invaded by MISC@1 troops repeatedly before .

It was built as part of the `` Festung Koblenz '' -LRB- Fortress LOCATION@4 -RRB- , by LOCATION@2 between NUMBER@1 and NUMBER@2 and guarded the middle LOCATION@3 region .
