How the U.K. is pressuring other nations into arming Ukraine

When it comes to supporting Ukrainian forces, the United Kingdom is trying to coax other nations into following its lead.

In the more than 15 months since Russian President Vladimir Putin invaded Ukraine, Britain has positioned itself as the leading supplier of advanced weaponry to President Volodymyr Zelenskyy's military. The U.K. was the first country to provide lethal aid to Ukraine and also the first to send advanced systems like Western tanks.

The U.K. wants Zelenskyy's forces to end Putin's invasion, but there is another goal, according to British officials.

They believe that Britain's shipments of sophisticated weapons have helped to pressure other governments, including the United States, that have sometimes hesitated. The British are also trying to shape the conversation about what new military capabilities Kyiv might need in the future.

"We’ve certainly been one of the leaders at nudging and encouraging others to have greater political courage," Tobias Ellwood, a conservative member of Parliament and the chair of its Defense Select Committee, told NBC News. "To look Russia in the eye — conscious of that escalatory ladder — and provide Ukraine what they needed."

The British government, though, can't support Ukraine alone militarily.

When London sent 14 Challenger 2 battle tanks to Ukraine in March, some analysts dismissed the move as merely symbolic. The number of tanks was too small to make a significant difference militarily and Ukraine does not have the supplies to support Challengers in the long term. But shortly after Britain dispatched its advanced tanks, Germany and the U.S. did as well.

Ellwood acknowledged that the Challenger tanks were not necessarily the system that Kyiv required, "but, in stepping forward, it allowed others to then follow suit."

The U.K. has also been among the first to provide other sophisticated weapons systems, including armored vehicles, multiple-launch rocket systems, light anti-tank weapons, short-range guided missiles and anti-aircraft missiles.

"The Brits have shown that when the Ukrainians need them," said William Taylor, a former U.S. ambassador to Ukraine, "they step up, bridge them up, and then others follow."

The U.K. is also the only nation to provide long-range cruise missiles, known as Storm Shadows, that can travel more than 150 miles, as well as drones that can fly over 125 miles. Some believe the systems could be the linchpin of a successful counteroffensive potentially aimed at cutting off Russia's land bridge to Crimea.

"For me, the most important thing is that at least somebody is getting Ukraine a capability that they need to make Crimea untenable for Russian forces," said retired Gen. Ben Hodges, who served as the commander of the U.S. Army Europe. "They have reconciled whatever concerns they have had about providing capabilities with this kind of range being used inside Russia — or whatever excuse the U.S. administration has not to do so."

The United States has so far provided more military aid overall to Ukraine than any other country by a wide margin. The U.K., the second-largest provider of military assistance, has committed $4.6 billion to Ukraine. Washington has committed $38 billion since Russia invaded.

None of the arm shipments by London were likely a surprise to the Biden administration. One current and one former British official said that all military aid to Ukraine has been closely coordinated with the United States. They said the U.K. would not ship weapons without approval from Washington.

Karen Pierce, the British ambassador to Washington, said the Biden administration was "very comfortable" with London's recent decision to provide Storm Shadow missiles, which have a longer-range than the missiles sent so far by the United States.

"We talk a lot to the U.S. We talk a lot to the Ukrainians. We talk a lot to our other friends and allies, and we collectively assess what capabilities Ukraine needs," Pierce said in an interview. The ambassador added that "each country makes its own decisions," and that "we don't see ourselves as setting an example."

A State Department spokesperson said that the U.S. and the U.K. work in close cooperation to help Ukraine but did not address questions about Britain's influence on the administration's decisions to deliver specific weapons systems. "We are grateful that the United Kingdom has taken a strong stand against Putin's war in Ukraine," the spokesperson said.

For the U.K., the dollar amount was never the point, British officials said. Instead, they hoped to break the diplomatic logjams that sometimes formed when countries feared that providing Kyiv greater capabilities could escalate tensions with Moscow and lead to a wider conflict.

"With the Storm Shadows it was the release of something long range and precision-guided that showed we were ready to take the next step," said Lord Admiral Alan West, who served as the chief of naval staff in the U.K. "And after that we spoke up and said we would train F-16 pilots. And I think that gave the Biden administration a way to look at this and say, ‘OK, we’re going to take this next move, too.’"

Britain's arms deliveries also countered claims that providing advanced weaponry was impractical because Ukrainian forces would be unable to effectively use and maintain it, according to Daniel Vajdich, president of Yorktown Solutions, a Washington consulting firm that advises Ukraine's state-owned energy sector and works with officials in Kyiv.

"There have been a number of instances where the Brits have been the first to announce, and that has pushed the U.S. and others to then be willing to discuss and ultimately deliver the weapon systems," Vajdich said.

Since Brexit, the U.K. has struggled to find its place on the world stage, Ellwood, West and other current and former British officials noted. But by throwing its weight behind Ukraine and trying to rally allies to back Kyiv, Britain has found a way to stay relevant as an international actor, a strategy that has produced political benefits at home.

Sending aid to Ukraine remains popular across Britain, according to a February YouGov poll. More than 80% of Britons said they supported Ukraine and 53% said the U.K. should continue its support until Russia withdraws from the country, no matter how long it takes. Ukraine is also seen as one of the few issues in Parliament supported by both Conservative and Labour leaders.

Still, British officials acknowledge that providing Ukraine with a patchwork of weapons will not lead to Russia's defeat in the long run. Eventually, some said, Ukraine will need to field a consistent series of military platforms — Leopard tanks on the ground and F-16s in the air, for example — rather than a mix of different hardware.

"We need to start discussing how to build the manufacturing capability of Ukraine to build their own kit," Ellwood said. "I think there's a sort of expectation with all these things that the penny hasn't really dropped yet. But this war is going to go on much longer than we think."

Phil McCausland is an NBC News reporter.

Dan De Luce is a reporter for the NBC News Investigative Unit.