But that's the thing - they can't spend those directly to buy tanks - until very recently, they were effectively forbidden from expanding their military capabil

But that's the thing - they can't spend those directly to buy tanks - until very recently, they were effectively forbidden from expanding their military capability, like Japan, and there is still a lot of political resistence against that sort of thing. So how do you forage a national defense industry then? You lend to others to buy their wares. That is only one of many, many German industries that would suffer from the demise of the Eurozone. The benefits of the common currency sustaining demand across the continent waaaaay outstrip any perceived "loss of control" for the German economy.