Complex sentence: Britain followed this traditional funding method--funding 90 per cent of its expenditures through borrowing--until 1798, but as the Napoleonic wars dragged on, Britain's massive expenditures rose to unprecedented levels.
Split into simpler sentences: Britain followed this traditional funding method--funding 90% of its expenditures through borrowing--until 1798. But as the Napoleonic wars dragged on, Britain's massive expenditures rose to unprecedented levels.