Europe Is Finally Ready to Spend More on Defense. The Hard Part Is How.

Around the globe, growth has been slowing, trade and investment have been falling, and now, escalating Middle East tensions are shaking up markets.

But governments across Europe and in Britain face an additional economic stress — significantly raising military spending. These peacetime economies have to figure out how to deter Russia, a belligerent foe that is already on a wartime footing and spending an estimated 7.5 percent of its national income on its military.

The debate has intensified in the run-up to the North Atlantic Treaty Organization’s annual summit meeting this week at The Hague, where the security alliance will set new spending goals. President Trump has demanded that the other 31 NATO members devote 5 percent of their total economic output to defense, up from the current 2 percent target. He has also made clear that the United States will reduce its financial and troop commitments, though it is unclear by how much.

This is a “global reset,” Lt. Gen. Sean Clancy, the new chief of the European Union’s military committee, said at a security conference in Brussels this month. But “we haven’t even defined what the transition looks like.”

Money, though, is far from the only issue Europe confronts now that it has reluctantly accepted the reality that it must be able to protect itself without help from the United States.

Formidable political, strategic and regulatory hurdles remain.

E.U. leaders must maintain public support for common military spending and joint weapons procurement, even as right-wing nationalist sentiments oppose giving the bloc more power.