Should Germany have built a fourth Sachsen-class air-defence frigate?
Short answerYes; three can sustain availability, but four provide a much more credible and resilient force.
NotesGermany would have benefited from more Sachsen-class air-defence frigates. A single hull is not a dependable force because maintenance or damage can remove the whole capability. Two ships provide the capability only when one is available, while three make routine availability more realistic. A fourth supplies the depth needed for a robust operational force.