Aerial photograph from Google Maps showing the star-shaped fortifications surrounded by a moat at Fortress Monroe
https://media.mstdn.social/media_attachments/files/113/859/157/286/935/533/original/49b2fbf5606e07f8.png
@Infoseepage @adapalmer It also has to do with fields of fire. Star-shaped fortifications give you two angles from which to shoot at or pour boiling oil on attackers. Here's Fortress Monroe, VA, a beautiful example that is still in use today (although not to defend against attackers).
https://www.google.com/maps/place/Fort+Monroe,+Hampton,+VA/@36.9983495,-76.3076793,613a,35y,351.79h,41.38t/data=!3m1!1e3!4m6!3m5!1s0x89ba853112971ded:0xcbbf5eda8390db5c!8m2!3d37.0171968!4d-76.2985941!16s%2Fg%2F1tfc2y15?entry=ttu&g_ep=EgoyMDI1MDExNS4wIKXMDSoASAFQAw%3D%3D
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