A new era of global rearmament is gathering pace, and it will mean vast costs and some tough decisions for western governments already struggling with shaky public finances.

Despite world defense spending reaching a record $2.2 trillion last year, European Union nations have only just begun to consider what 21st-century security will require with an aggressive Russia stirring on their eastern borders, a volatile Middle East, and the expansion of the Chinese military tugging Washington’s attention toward the Pacific.

Political leaders have been congratulating themselves on progress toward NATO’s targets for members of the alliance to set aside 2% of their gross domestic product on defense. But officials focused on security say that military budgets may need to emulate Cold War spending of as high as 4% in order to deliver on the alliance’s plans.