NATO's European members have pledged a significant increase in their military spending to strengthen Donald Trump's support for the alliance. The leaders committed to a target of 5% of GDP, but experts warn that such a level is difficult to achieve and economically burdensome.
"They won't get there", Guntram Wolf, a senior fellow at the Bruegel think tank, said of the 5% target.
"If you are a heavily indebted country, you can't issue more debt, that means very difficult budgetary decisions," he said of the large tax increases or spending cuts that would require.
As a piece of political theater, the Hague summit at least won over its intended audience: Trump himself. Amid concerns about his commitment to NATO's mutual defense clause, he said the United States stood by its European allies "all the way," Reuters reported.
While few would dispute that Europe needs to do more to ensure its own security as tensions with Russia rise, the fixation on the 5% target has cut off a separate debate over how the bloc could use its existing military budgets more effectively, for example through joint procurement agreements between national governments.
Europe has now burdened itself with promises that - with the exception of Germany, whose finances are sound after years of fiscal austerity - will be difficult for most members to keep.
To reach the 5% threshold, European Union countries, whose debt already exceeds 80% of GDP, would need to collectively almost triple their The 325 billion euros it spent on defense last year to more than 900 billion.
Britain - whose debt is 100% of GDP and which already pays more on debt service than on any other expenditure except health - will need an additional 30 billion pounds.
"The potential losers are not only future generations, burdened with huge debts, but also today's societies," said Nick Whitney of the European Council on Foreign Relations.
"A disaffected population, whose sense of economic well-being has never recovered from the global economic crisis of 2008, is likely to become even easier prey for populist or nationalist politicians gaining strength across Europe."
Spanish Socialist Prime Minister Pedro Sanchez - whose country is the only one that has not explicitly signed up to the new target - it voiced the concerns of other members when it said the target was "incompatible with our welfare state".
Slovakia, one of the central European countries whose budgets face the greatest strains from building up defence resources, has also opposed the target, arguing that raising living standards and reducing borrowing are equally important.
Bruegel's Wolf said it remained to be seen whether countries would increase their defence spending by cutting a few billion from other areas, or whether large areas such as pensions would take a significant hit.
"But keep the proportion - there will still be a welfare state, but perhaps a less generous one," he said of social protection across Europe, which could account for up to 30% of the economy.
5% is divided into 3.5%, which will be spent on "core" defence - troops and weapons - and 1.5% for defence-related measures, such as adapting roads and bridges to accommodate military vehicles. The option of including existing expenditure items in the latter category is likely to prove generous.
In France, for example, there is discussion about whether this could include the gendarmerie, which patrols rural roads, which are officially part of the defence ministry but whose existing running costs are currently outside the overall defence budget.
The long timescales announced for achieving the target - in some cases up to a decade - also mean that these promises could be undermined as the political spotlight shifts elsewhere.
"The spending targets simply won't be met," Whitney said. "The necessary transformation will begin to take shape, but more slowly and inconsistently than if more realistic goals had been set."