Florence commissioned Niccolo Machiavelli in 1526 to prepare a report on upgrading town defenses. He recommended three ways to address the situation:
Cost for any included labor and materials but, especially in the case of #2, the value of useful property sacrificed for defense. That property could include economically important mills, furnaces, and warehouses.
The new Trace Italienne mode was the best solution, but ideally had to employ either point #1 or #2. Should financial resources not be up to that degree of defense, then the next best thing had to be utilized. But what has been discussed so far was adapted and compromised to be applied as best as possible to Machiavelli's #3, which was by far cheaper and faster to do. But it was the weakest. Cheap and fast apparently appealed to many towns because it made do from the Mediterranean to the Baltic - even if some builders never read that report.
A town fortified in the old-style was retrofitted with this bastion topped with gabions (in brown). The palisade in the moat was likely also a late modification.
Outdated fortifications and town walls could also be strengthened with new outerworks. That's discussed a few pages later.
If done sufficiently, the resulting defenses could hold up in a siege. Witness Metz, 1552, in which the besieging Imperial forces of 55,000 soldiers were eventually compelled to call it quits. On the other hand, the Duke of Parma's Army of Flanders took one Dutch town after another simply because their defenses were incomplete or inadequate or both (95 in all).
Built the Fort