This is part one of a series examining the challenges facing the NATO Alliance.
As President Donald Trump ramps up pressure on NATO allies to increase defense spending — and orders the withdrawal of 5,000 U.S. troops from Germany over the next six to 12 months — a deeper issue is coming into focus: Even as allies’ budgets rise, NATO is still heavily dependent on U.S. military power to function.
Kellogg, who served as a senior national security official during Trump’s first term, said the alliance has expanded politically but not militarily — creating what he says is a growing gap between commitments and actual capabilities.
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NATO Secretary General Mark Rutte, US President Donald Trump and British Prime Minister Keir Starmer pose with leaders of NATO countries during the NATO Heads of State and Government Summit in The Hague, Netherlands, on June 25, 2025. (Ben Stansall/Pool/Reuters)
“You started with 12, and you went to 32, and along the way I think you diluted the impact,” he argued, calling today’s NATO “a very bloated architecture.”
But not everyone agrees that the alliance is losing relevance.
“It has never been more relevant,” said John R. Deni, a research professor at the US Army War College, who says NATO remains central to US national security.
“The reason for that is twofold,” he said. “First of all, it’s our comparative advantage over the Chinese and the Russians… they don’t have anything like that.”
“And the second reason… NATO endorses the security and stability of our most important trade and investment relationship,” he added, referring to economic ties between North America and Europe.
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Dependence: Design or Weakness?
Around 2010, the United States accounted for roughly 65% to 70% of NATO’s defense spending, according to an analysis by Barak Seener of the Henry Jackson Society, a London-based think tank.
“They have always been dependent on the US,” Kellogg said of the European allies.
“The allies generally rely on each other for deterrence and defense by design,” Deni said, explaining that alliances exist to “pool their resources” and “pool their individual strengths.”
Deni cited ground forces as a clear example of what the U.S. is getting out of the alliance, noting that “there are far more Allied mechanized infantry forces on the ground than there are Americans.”
Still, he acknowledged that trust has sometimes gone too far.
“In the past… it was fair to say that European allies were too dependent on the Americans for their conventional defense,” he said, pointing to the 2000s.
That, he said, was driven in part by American priorities — as Washington pushed European allies to focus on wars in Afghanistan and Iraq rather than territorial defense.
A Polish Army soldier sits in a tank as a NATO flag flies behind him during the NATO Noble Jump VJTF exercises on June 18, 2015 in Zagan, Poland. (Sean Gallup/Getty Images)
Seener describes NATO as “formally collective, but functionally asymmetric,” with the US providing a disproportionate share of “high-end capabilities.”
This asymmetry is most visible in nuclear deterrence.
Seener said the U.S. supplies the vast majority of NATO’s nuclear arsenal — including intercontinental ballistic missiles, submarine-launched systems and strategic bombers — meaning deterrence ultimately depends on the assumption of U.S. retaliation.
“The good news,” the official added, “is that the Allies are doing just that. They are acting and working together – and with the US – to ensure that together we have what we need to deter and defend a billion people in the Euro-Atlantic area.”
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Boeing CH-47 Chinook helicopters from the U.S. Army’s 12th Combat Aviation Brigade fly over a Lithuanian Vilkas infantry fighting vehicle during the Allied Spirit 25 military exercise near Hohenfels, Germany, on March 12, 2025.
The systems that NATO cannot replace
In addition to nuclear weapons, dependence also runs through the operational backbone of the alliance.
Seener pointed out that US-provided intelligence, surveillance and reconnaissance – as well as logistics and command systems – are essential to NATO operations.
“Without US intelligence and surveillance, NATO loses situational awareness and early warning ability,” Seener said, adding: “So that means Russia, for example, could attack Europe. And theoretically, if there is no NATO and the US is not involved, Europe would not be aware, otherwise it would take too long to be able to defend itself.”
Kellogg also says that much of Europe’s military capability does not meet top-level systems.
“For the most part, their equipment, if you had to give it an A, B, C, D, E, F, is kind of B players or C players,” he said. “It’s not the first work.”
He pointed to air and missile defense as a key gap, noting that while European countries rely on U.S.-made systems such as Patriot and THAAD, “they don’t have a system that is comparable.”
Kellogg attributed that to years of underinvestment and said Europe’s defense industry has “withered away,” adding that the United States is now “relearning” that too.
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NATO Secretary General Jens Stoltenberg looks on as President Donald Trump and Polish President Andrzej Duda talk during a working lunch at the NATO Leaders’ Summit in Watford, Britain, on December 4, 2019. (Kevin Lamarque/Reuters)
Deni said the picture is more mixed today.
“The Alliance’s defense spending has increased… and will increase much further after 2022,” he said, pointing to Russia’s 2014 invasion of Crimea as a turning point.
But he cautioned that gaining capacity takes time, noting that many improvements are still years away from full implementation.
Deni pointed to recent European purchases of US systems as evidence of growing capacity, noting that countries including Poland, Romania, Norway and Denmark are adopting the US F-35 fighter jet
“You can’t build an F-35 overnight,” he said, adding that it will take years for many of these improvements to be fully realized.
Keith Kellogg speaks at the Warsaw Security Forum 2025 on September 30, 2025 in Warsaw, Poland. (Marek Antoni Iwanczuk/NurPhoto via Getty Images)
The official said the priorities include air and missile defense, long-range weapons, logistics and large land forces, noting that while the details remain classified, the plans call for a fivefold increase in air and missile defenses, “thousands more” armored vehicles and tanks, and “millions more” artillery shells. NATO also aims to double key support capabilities such as logistics, transport and medical support.
The official added that allies are increasing investments in warships, aircraft, drones, long-range missiles, as well as space and cyber capabilities, while increasing readiness and modernizing command and control.
“These objectives are now included in national plans,” the official said, adding that allies must demonstrate how they will achieve these objectives through sustainable defense spending and capability development.
The NATO official also noted that European allies lead multinational forces in Central and Eastern Europe, while the US and Canada serve as framework countries in Poland and Latvia, in addition to ongoing air policing missions and NATO’s KFOR operation in Kosovo.
One of the Swedish Air Force’s three JAS 39 Gripen fighter jets takes off from the Blekinge Wing F17, based in Kallinge, southern Sweden, to a base in Sardinia on Saturday, April 2, 2011, to take part in the NATO-led operation in Libya. Now that Sweden is joining NATO, the country is saying goodbye to more than two centuries of neutrality. (AP Photo/Scanpix/Patric Soderstrom, file)
What happens if the US is stretched?
Kellogg’s warning is direct: NATO’s deterrence depends on the American presence.
“The thing you always have to worry about… is Russia,” said Kellogg, Trump’s 2025 special envoy to Ukraine and Russia.
If US forces are tied down elsewhere, NATO could face serious tensions – especially in areas such as intelligence and logistics.
For Kellogg, there is a danger of delay. “We won’t know until it happens,” he said. “And then you can’t respond to it anymore.”
However, Deni said the alliance remains a strategic asset – not a liability.
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A NATO force stands guard outside the World Forum in The Hague ahead of the two-day NATO summit on June 22, 2025. (Remko de Waal/ANP/AFP)
The question, he suggests, is not whether NATO still works. What matters is whether the allies can adapt quickly enough to keep the situation going.
