AFP Photo: Ludovic Marin

Ahead of the NATO summit in London, marking the 70th anniversary of the alliance’s founding, a remarkable war of words broke out among political leaders.

It started with the president of France, Emmanuel Macron, calling the alliance “brain dead,” a diagnosis that prompted immediate responses from political leaders across the continent. Germany’s Angela Merkel called it “drastic”; Estonian leaders, who see NATO as the only guarantee against Russian aggression, said it sent a “dangerous signal.” Donald Trump waded in, calling Macron’s words “insulting” and “a very dangerous statement” to make.

Such heated words are merely flotsam on the waves; below the surface there are powerful currents pulling the alliance apart.

Macron’s utterance is only the latest expression of exasperation by political leaders over NATO’s purpose. Most crucially, questions have been raised about the viability of NATO’s Article 5 mutual-defense clause, whereby an attack on one member is considered an attack on all. This clause is the central part of the alliance; without it, NATO would become a club for powerful countries only, an alliance for the few. If NATO will not defend the interests of weaker members, it has no business existing at all.

Macron managed to anger many members of the alliance before the summit by openly questioning whether NATO would come to the aid of member countries. “If the Bashar Al Assad regime decides to retaliate against Turkey, will we commit ourselves under [Article 5]?” he asked, apparently rhetorically.

The question was asked about Turkey, but the answer applies across the entirety of Europe’s borders. In particular, the Baltic states of Latvia, Lithuania and Estonia, which, since the annexation of Crimea have become the focus of NATO’s training exercises, were concerned at this dilution of the mutual-defense guarantee.

This is the second time in as many years that NATO’s collective security has been challenged. Last year, US president Donald Trump publicly questioned whether America would respond if Montenegro, one of the smallest NATO countries by population, were attacked. That’s why Macron’s question, taken together with other comments on Turkey, are so worrying, because they are not aimed merely at one country, but because they undermine the entire architecture of collective security. If NATO won’t respond to Ankara, why would it help the Baltic states, or anyone else?

It’s particularly important because Article 5 has been invoked only once, under the most dramatic of circumstances, when the strongest member of the alliance suffered its worst terror attack on September 11, 2001. The question is whether smaller countries could expect the same solidarity under less dramatic circumstances.

At the same time as questioning his commitment to Article 5, Macron wants greater assistance from NATO members in the Sahel, where France has just suffered its worst combat casualties for nearly 40 years. Macron seems particularly sensitive about it, explicitly linking the deaths of 13 soldiers during a helicopter crash in northern Mali, where the French army is fighting jihadists, with Washington’s insistence that NATO allies pay more. “In the Sahel, France is involved and acting on behalf of everyone,” Macron said last week. “If some people want to see an example of what they term cost-sharing, they can come to the ceremony” for the dead soldiers. “There they will see the cost.”

This creates a sense that Macron, the head of one of the world’s most powerful militaries, wants NATO to assist France, but is unwilling to commit the alliance to assisting other members – particularly those, like Turkey, on the geographical periphery. And it is particularly galling given that France, in common with many of Europe’s richest countries, does not pay its fair share to NATO.

On this, Donald Trump is right. He has been blunter than previous US presidents in demanding NATO members pay their dues, but he is asking an essentially reasonable question: why should the US, which after all could defend itself without NATO, pay over the 2 percent of GDP that is the NATO requirement, when Germany, Europe’s biggest economy but without the military heft of France or Britain, pays less, yet benefits from the security umbrella?

In fact, according to NATO’s own figures, some of the largest European countries are freeloading on the backs of the smaller ones. Apart from the UK and the US, which pay over the 2 percent target, not a single one of the next five richest European countries meets that target. By contrast, Latvia, Lithuania and Estonia, all small countries with comparatively modest GDPs, do meet the target.

Montenegro, the country Trump was not sure whether he would defend, pays more as a percentage than Germany, Italy or Spain. As does Turkey.

The effect, then, is that some of the smallest countries are subsidizing the richer ones, at the same time as political leaders question whether these countries would actually get anything for their money. In effect, they are paying for an insurance policy they can never use.

The debate over Article 5 and its future place in the alliance goes to the heart of whether NATO is working as intended and whether it can continue in its current form. The squabbling among political leaders is the sound and fury, but it signifies a sense of drift in the institutions, a lack of certainty in the system.

That system only works if smaller countries like Estonia or Montenegro really are under NATO’s umbrella. If NATO is not willing to defend its smaller members, and even Turkey, if it were to ask for assistance, then the alliance is merely a subsidized security scheme for rich countries. That would leave NATO not merely brain dead, as Macron alleges, but, in Trump’s words, as Trump obsolete.

Faisal Al Yafai is currently writing a book on the Middle East and is a frequent commentator on international TV news networks. He has worked for news outlets such as The Guardian and the BBC, and reported on the Middle East, Eastern Europe, Asia and Africa.