Poznań Fortress , known in German as Festung Posen ( Polish : `` Twierdza Poznań '' ) was a set of fortifications in the city of Poznań ( German : `` Posen '' ) in western Poland , built under Prussian rule in the 19th and early 20th centuries .
Poznań Fortress ( in Polish : `` Twierdza Poznań '' , in German : `` Festung Posen '' ) was a set of fortifications in the city of Poznań in western Poland , built under Prussian rule in the 19th and early 20th centuries .