The 16th and 17th were quiet .
On the 18th the fort came under heavy bombardment , returning harassing fire from the fort 's 75mm guns , which had so far been unaffected by the German fire .
The 16th and 17th were quiet , but on the 18th the fort came under heavy bombardment , returning harassing fire from the fort 's 75mm guns , which had so far been unaffected by the German fire .