4/11/2019 Fort Pulaski. At the time this place was constructed, it was assumed that it was impenetrable. 11 foot thick, solid brick walls were no match for cannons that were available at the time. Then, as they always do, times changed and weapons improved. This was the first fort to be attacked with rifled cannons and the effects were devastating. The fort was surrounded after just 30 hours of battle and had sustained heavy damage.