Technically speaking, it was accurate indirect-fire artillery which killed the fortification. 18th and 19th century fortifications were quite effectively designed to deal with direct-fire artillery, by the simple expedient of MASSIVE earthworks between the fort walls and the opposing artillery. Sadly, there are very few surviving examples of the intricate earthworks built around the star forts of the 18th century, but essentially the primary defensive mechanism against artillery was a burm built up to the height of the fortress walls, low enough that artillery inside the fort could fire over it, but high enough to make direct fire against the walls all but impossible.
Which was why so few battles ended with storming of fortifications. It was VERY difficult to take a star fort, so typically what one did was wait a predetermined time for the defenders to surrender (usually dictated by the estimated amount of food in the fort), at which point the defenders, having made their token defense, were permitted an honorable surrender, disarmed, and allowed to march home. Of course, if you forced an opponent to storm the fortification you could expect no mercy for anybody inside.
It was accurate plunging fire that made the massive, permanent, fortification less effective.
Field fortifications, however, are still quite common and very useful.
Could you kindly clarify that?
