Star Fort - Construction

Construction

There were huge costs involved in creating the fortifications, with Amsterdam's 22 bastions costing it 11 million florins and Siena in 1544 bankrupted itself to pay for its defences. As such, they were often improvised from earlier defenses. Medieval curtain walls were torn down, and a ditch was dug in front of them. The earth used from the excavation was piled behind the walls to create a solid structure. While purpose-built fortifications would often have a brick fascia because of the material's ability to absorb the shock of artillery fire, many improvised defenses cut costs by leaving this stage out and instead opted for more earth. Improvisation could also consist of lowering medieval round towers and infilling them with earth to strengthen the structures.

It was also often necessary to widen and deepen the ditch outside the walls to create a more effective barrier to frontal assault and mining. Engineers from the 1520s were also building massive, gently sloping banks of earth called glacis in front of ditches so that the walls were almost totally hidden from horizontal artillery fire. The main benefit of the glacis was to deny enemy artillery the ability to fire point blank. The higher the angle of elevation, the lower the stopping power.

The first key instance of trace italienne was at the Papal port of Civitavecchia, where the original walls were lowered and thickened because the stone tended to shatter under bombardment.