In front of the Perches redoubts, the Bosmont, whence the Prussian engineers began their attack, is now heavily fortified with continuous lineslcalled the Organisation defensive de Bosmont.
The Perches ridge, whence the town and suburbs could be bombarded, he fortified with all possible speed.
The Perches ridge was crowned with a parallel and numerous batteries, which in the end mounted ninety-seven guns.
Poles or perches; 4 roods= i acre.
On the night of the 20th of January the French lines about Perouse were carried by assault, and, both flanks being now cleared, the formal siege of the Perches forts was opened, the first parallel extending from Danjoutin to Haut Taillis.