Sweden and Denmark are pouring money into defense, tightening ties with each other and Europe—and moving beyond the U.S. It’s paying off. COPENHAGEN and STOCKHOLM—Sweden’s central bank has been worrying about what cashless consumers would do if an emergency such as a Russian cyberattack took down the electrical or communications grid. And so as of July, Swedish consumers can buy essential goods using their Mastercard and Visa cards without a network connection. The central bank (the Riksbank) wants to go further by enabling offline purchases with Swish, a local mobile payments system that bypasses the Visa and Mastercard networks altogether....