They replaced the old small castles on high ground protected only by wooden stockades with large central fortresses out of range behind broad moats, surrounded by solid stone ramparts and earthworks strong enough to resist cannon fire.
The traditional castles were kept as they were but additional ones were also built.
mnli hypothesis: The traditional castles were kept as they were but additional ones were also built. premise: They replaced the old small castles on high ground protected only by wooden stockades with large central fortresses out of range behind broad moats, surrounded by solid stone ramparts and earthworks strong enough to resist cannon fire.