BRUSSELS (AP) — NATO leaders will gather in London today as the world’s biggest military alliance, marking its 70th birthday, battles with one of the most confounding of adversaries: Itself.

As thousands of troops stand ready along Europe’s eastern flank to deter Russia — the reason the trans-Atlantic alliance was founded in 1949 — or help keep the peace in places like Afghanistan and Kosovo, the leaders of countries with NATO’s largest armies are wildly taking pot shots at each other.

Before the two-day summit, to include receptions at Buckingham Palace and Downing Street plus a working session at a golf resort in outer London, Karen Donfried, president of the German Marshall Fund think tank, said the 29 NATO allies are approaching this meeting “with a sense of foreboding.”

“Few anticipate a gathering that will both unify and stop the growing cracks in cohesion. Alliance leaders carry the responsibility to articulate NATO’s common purpose and ongoing relevance. If they do not, Vladimir Putin will be raising a glass in Moscow to the fraught state of the alliance at 70,” she said, in reference to Russia’s president.

In recent months, U.S. President Donald Trump has declared that peace is nigh in Afghanistan — NATO’s longest and most costly operation in terms of lives and cash — only to call off talks with the Taliban. Now, it seems, they are on again. All the while, U.S. troop numbers are declining. Other allies are unsure what to make of it.

Last month, he precipitously pulled troops out of northern Syria. Turkey took that as a green light to launch an invasion that has alarmed its European NATO partners, many already struggling with the political fallout sparked by the arrival of tens of thousands of Syrian refugees via Turkey in 2015.

French President Emmanuel Macron, complaining of a U.S. leadership vacuum and sensing an opportunity for France to fill it and boost Europe’s security credentials, has lamented the “brain death” of NATO and says the allies need “a wake-up call.”

Macron wants strategic talks about where NATO is going, who its adversaries really are, how to tackle terrorism, what to do about an unpredictable ally like Turkey, and how to improve relations with Russia, rather than a spend a third summit in self-flagellation about Trump’s favorite topic: military spending.

In the latest act of political friendly-fire, Turkey accused Macron of supporting terrorism for agreeing to hold talks with a Syrian Kurd politician whom Ankara considers to be part of an extremist group.

“You should get checked whether you’re brain-dead,” Erdogan said Friday, in remarks directed at Macron. “Kicking Turkey out of NATO or not, how is that up to you? Do you have the authority to make such a decision?”

Meanwhile, Erdogan plans to test a new air defense system, purchased from Russia, that its partners refuse to allow near any NATO military equipment.

German Chancellor Angela Merkel, in the final period of her reign, has played the go-between, trying to keep the NATO leadership train on the rails.

From the outside, and quite possibly from the Kremlin, it looks like a great act of self-harm.

NATO has no real wars to fight but its power, and Europe’s security, lies in the abilities of the allies to deter adversaries like Russia and potential ones such as China. That deterrence depends on a balanced mix of military posturing and shows of political resolve by speaking with one voice.