Between 1870 and 1914 the French did not only construct large forts in the Alps, but also smaller blockhouses. These buildings had several levels with embrasures all around. They usually served as a reduit for some nearby batteries. The blockhouse of Janus (1886-1889) was a small exception. This position was exception because here a large casemate for four 95 mm guns was later added. The blockhouse of Janus was damaged by the Italian artillery during the fightings in June 1940.