Star Forts

In Sweden the central part of the city of Gothenburg still has parts of the star fort left:

https://goo.gl/maps/hsn3fQWB61B2

And the castle of Landskrona has multiple layers of star fort shaped moats and walls.

https://goo.gl/maps/aAAb2fACJDt

>Historians enjoy debating the scope of the word, but usually accept a castle to be the private fortified residence of a monarch or nobleman. This definition excludes fortresses, which were not homes, and also fortified towns, which were public defences rather than private residences. Taking a little licence we can extend the definition to buildings that might not technically qualify under this definition

Very, until firepower significantly increased and powerful long range direct hits with piercing high explosive shells as well as ballistic shots (mortar, long range artillery) would just render the defence moot. From the article:

> Fortifications of this type continued to be effective while the attackers were armed only with cannons, where the majority of the damage inflicted was caused by momentum from the impact of solid shot. While only low explosives such as black powder were available, explosive shells were largely ineffective against such fortifications. The development of mortars, high explosives, and the consequent large increase in the destructive power of explosive shells. Plunging fire rendered the intricate geometry of such fortifications irrelevant. Warfare was to become more mobile

You can see this in WW1 (e.g battle of Verdun), where battlefields and front lines are very spread out and mobile[0], and key points like forts[1] are out of town, have much simpler geometry, and are dug deep to protect from artillery. Also, growing use of reinforced concrete.

Trivia: there was a level on C&C 3 (GDI Mission 10, Sarajevo) that I remember playing and as the map unfolded I saw that this was actually sort of a Vauban fort!

[0]: https://en.wikipedia.org/wiki/Battle_of_Verdun#/media/File:G...

[1]: https://en.wikipedia.org/wiki/Battle_of_Verdun#/media/File:F...

[2]: https://youtu.be/hPmhXC41mUQ?t=1575

James Burke covered this a bit in episode 9 of Connections (about 4 minutes in):

https://archive.org/details/james-burke-connections_s01e09

Fortified buildings of that era tended to be very functional, though I agree they can also be quite beautiful in shape.

One advantage of the angular bastion shape is that the triangular point does not allow for a dead zone created by circular bastions, where enemy troops can hide at the base of the wall and undermine it while concealed from most defensive fire by the bastion itself.

Normally the bastions are not just an outward triangular point, but angle back inwards on the curtain wall side as well. This would allow defenders to bring enfilading fire along the curtain wall should the attackers get that close, without being subject to direct fire from attackers further out.

Combined with the presence of a wide ditch with a glacis to the outer side and the thicker and sloped lower walls on the inner side, this made any approach to the main curtain wall, either to undermine it or to scale it, extremely difficult and dangerous for the attackers.

In addition to the angular bastions, star forts typically featured separate ravelins. These also served a number of useful functions, not least providing a relatively safe forward firing position that was protected from the front but left exposed on the curtain wall side in the event that the position was overrun and its defenders retreated. Even if they fell, their shape and position would force enemy forces to divide before reaching the main wall, and they also provided some additional protection against incoming cannon fire for the curtain wall behind, helped by being set on a different angle as you mentioned.

These tactical advantages remained relevant for quite a long period in military history, from the first star forts in the 15th century until around the 18th. They rapidly faded after that, however, as the introduction of indirect fire weapons like mortars and high explosive shells rendered the intricately shaped defensive fortifications obsolete.

Fort Monroe is a 7 pointed star fort at the mouth of the Chesapeake Bay.

https://en.wikipedia.org/wiki/Fort_Monroe

https://www.google.com/maps/search/fort/@51.2143117,4.488975...

https://en.wikipedia.org/wiki/Race_to_the_Sea#/media/File:DE...

https://en.wikipedia.org/wiki/Fort_George,_Highland