What would much higher British defence spending achieve, and how much is sustainable?
Short answerAbout three percent of GDP could restore hollowed-out capabilities, while six to ten percent in peacetime would be unnecessarily expensive and disruptive.
NotesSpending six to ten percent of GDP in peacetime would buy more equipment than Britain could use efficiently and would require unpopular cuts elsewhere. Historically, four to five percent was more typical when danger was close, while very high shares belonged to imminent or actual war. For the conditions discussed here, the proposed level is roughly three percent, calculated without loading pensions, war graves, portions of research, or foreign aid into the headline total. The immediate purpose would be to restore personnel, stocks, maintenance, and force depth that repeated cuts had left nominally present but operationally thin. A credible capability requires the capacity behind the label.