A year on from their historic pledge to ramp up defence spending, leaders of the North Atlantic Treaty Organisation (Nato) gathering in Ankara next week will reckon with another challenge: getting industry to produce enough weapons. As money flows into defence budgets — up $90 billion in Europe and Canada last year alone — the 32-nation alliance is struggling to transform the funds into firepower. “Cash is crucial, but you can’t stop a missile or a tank with a dollar or a euro,” Nato chief Mark Rutte said.