The defensive fortifications of medieval times have surely inspired floorplans for the “perfect castle” in the minds of many a young nerd—replete with battlements, parapets, turrets, arrow slits, a keep, and of course murder holes.
As with all technologies though, including castle fortifications, they tend to go obsolete with new developments. With the advent of black powder in early modern Europe, from as early as the 15th century, the medieval fortress became outmoded as cannons rolled onto the scene.
The stone walls of medieval castles shattered upon impact from cannon fire. Their high walls and square construction, when hit perpendicularly, made them extremely fallible targets. Thus, a new advancement in defensive warfare was born, namely: the bastion fortress, also called the star fortress.
It basically all began in Italy with the defense of Pisa in 1500. Assailed by the Florentine and French armies, the Pisans realized that by backing their curtain wall with an earthen rampart, the impact from cannon fire was mitigated and absorbed. Then in 1509, at the siege of Padua, monk engineer Fra Giocondo had the city’s medieval outer wall cut down and a wide ditch dug with projections extending into it housing gun ports. These could then strafe attacking parties with direct and devastating flanking fire. The besiegers were repelled and bloodied, and they eventually retreated.
Such applications led to the advent of a new type of fortress—one that was lower and larger than previous constructions, covering more ground. The Italian engineers who developed it were sought out from across Europe during the 1530s and 1540s, hence it also garnered the name “trace italienne,” or “Italian outline” in French. The star fortress was born and continued in its development for three centuries, eventually being taken to its logical extreme in the late 17th century by military architects under Louis the XIV.
Exemplifying this architecture, Fort McHenry in Baltimore, Maryland, was erected in 1798 which famously inspired “Star Spangled Banner,” America’s national anthem, penned by Francis Scott Key following the War of 1812.
Like the turrets and murder holes of the medieval castle, a whole new set of implementations and strategies evolved in the star fortress.
The tall, square, stone curtain wall, once easily shattered by cannon, was replaced by brick and earth—or simply earth alone—which could absorb the impact of such ordinances. The wall had a lower profile now to present less of a target, and the ditch was correspondingly dug lower to stop an enemy from scaling the stouter wall. The ditch was also widened so that infantry troops were more exposed to defensive attacks from above.
Additionally, an earthen slope called a glacis descending outward from the outside of the ditch mitigated point-blank artillery fire directed inward. The lower the glacis’ angle of elevation, the greater its stopping power was.
Naturally, the most remarkable features of the star fortress are its points—its long, diamond-shaped bastions situated at various intervals surrounding its inner structure. These form large, angular surfaces presenting fewer perpendicular targets for an enemy. A cannonball was more likely to glance off them or be absorbed, whereas perpendicular medieval curtain walls were highly susceptible to direct attacks.
These pointed bastions also made the best possible use of positioning to flank enemies trying to storm the outer wall, which was highly vulnerable for attacking cannons should they occupy the glacis. They also eliminated “dead zones,” areas where attackers were relatively concealed from fire due to the defenses’ geometry. For example, defenders in older castles could not fire around curved towers, so these were extended to form points, thus eliminating all cover for invading troops.
Indentations called enfilades at the base of each point on the star would allow defensive cannons a clear line of fire down the edge toward neighboring points. Troops who made their way into the ditch attempting to breach the outer wall found themselves in “kill zones” (much like in medieval times) where attackers were left without cover, often exposed to fire on multiple fronts.
Evolving into more sophisticated configurations, the star fortress was taken to its pinnacle: bastions were extended further and formed into even more complex hornworks, crownworks, or even separate fortresses entirely detached from the central structure.
Bastion forts made use of intricate shapes with interlocking fields of fire to ultimately resolve many of the deficiencies of the medieval fortress in a new age of warfare.
Yet, as new technologies emerged on the scene with the advent of high explosives and mortars, star fortresses, too, fell into obsolescence. As plunging fire and high-explosive rounds appeared, they became increasingly irrelevant and were replaced by simpler but stouter polygonal bases. Many were eventually turned into tourist attractions and museums, such as Fort Wood in Upper New York Bay which became the foundation of the Statue of Liberty on Liberty Island—There’s still a ton to love about these places!
Indeed, warfare itself evolved to become more mobile and less dependent on static defenses and fortifications. Just as tube televisions, VHS video cassette tapes, and medieval castles saw their usefulness slip away, the still-impressive star fortress also outlived its heyday.
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