My grandfather’s U.S 2nd Inf went up againist two German fortifications, the Atlantic Port garrison of Brest and the Westwall. During both operations he was under his worst bombardments.
Brest was tough objective to take. Like Cherbourg it was a major port, and as such it was heavily defended by the Germans, who wanted to keep Atlantic ports out of Allied hands for as long as possible, thus restricting their ability to bring in the massive supplies they needed (much of which had to come in through the Normandy beachhead for quite a long time). Brest also got heavily bombed prior to the D-Day invasion, owing in part to the large U-boat pens which were located there (and which are still used today by the French Navy). By the time the Allies had liberated Brest (I believe in September 1944), a large percentage of the town had been smashed to rubble. I visited Brest a few years ago, and I brought back as a souvenir a book of before-and-after photographs showing various places in old Brest and their current appearance today. Brest had to be rebuilt very quickly, so much use was made of concrete and little attention was paid to historic preservation or architectural elegance. The town nowadays looks rather bland as a result.