It could be the world's most powerful telephone.
By the White House's telling, the now near certain addition of militarily non-aligned Finland and Sweden to NATO, transforming the European security landscape and defying Russia's power play in Ukraine, all came down to a series of quiet calls from President Joe Biden.
As Moscow massed troops for its February invasion, Biden "realised that we were on the cusp" of a new world, a senior US official said. So he dialled up Finland's president to discuss expanding NATO right to Russia's border.
More calls followed.
Then there was an Oval Office meeting with Finnish President Sauli Niinisto in March -- by which time Russian troops were pouring into Ukraine. And one more fateful call.
"The two leaders actually picked up the phone there on the side table in the Oval and called out through the White House Situation Room to the Swedish prime minister," the official said, briefing reporters on the behind-the-scenes details. They "got her on the phone at about 10 o'clock at night."
Ukraine's President Volodymyr Zelensky called for the United Nations to visit the site of a missile strike on a shopping mall in the city of Kremenchuk, as he addressed the UN Security Council on Tuesday.
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The rest, as the official said, "is history".
Actually, there was still more work to be done: Turkey was threatening to veto the expansion for its own complicated internal reasons. So Biden once more worked the phones.
Before arriving in Madrid for the NATO summit Tuesday, he called Turkish President Recep Tayyip Erdogan and they "talked through" the concerns. Later, he exchanged with the leaders of both northern European countries.
The deal was done.
Not just Finland, but Sweden will abandon military non-alignment and join a newly invigorated NATO, effectively telling Russia's President Vladimir Putin that his attempt to weaken the West has been a bust.
"That's exactly what he didn't want," Biden said in Madrid on Wednesday.
He was beaming.
"None of this would have happened, at least to the same degree, without massive US pressure, including from Biden personally," said James Jeffrey, a former US ambassador to Iraq and Turkey who now works at the Wilson Center.
"He and America are having a very good week in Europe."
Flexing US muscle
Allies may be aghast at the turmoil inside the United States.
Mass deaths of migrants in the Texas heat, societal war over abortion and guns, and lurid allegations in the January 6th hearings of Donald Trump throwing food at the wall in frustration as he stoked insurrection -- a lot's happening back home.
And Biden, whose Democratic party is likely to lose control of Congress in November, appears increasingly powerless to impose his will.
Across the Atlantic, though, the veteran US leader is flexing the kind of muscle that no other Western leader can match.
In addition to the expansion of NATO, Biden announced Wednesday a major beefing up of US hardware in Europe: two more squadrons of F-35s in Britain, two more naval destroyers in Spain, an additional brigade in Romania, a permanent army headquarters in Poland.
"Air, land, maritime, cyberspace -- the whole swath of US military capabilities," White House spokesman John Kirby said.
That bristling array of firepower folds into NATO's startling overall pledge to augment the current multinational rapid reaction force from 40,000 to more than 300,000 troops, as well as movement towards assuaging longtime US demands for Europeans to foot their share of the military bill.
Also, while most of the focus is on countering Putin's Ukraine invasion, NATO has for the first time named China as a strategic challenge -- another key US priority.
Jeffrey says Biden is demonstrating the unique US role, where "nothing" can happen without Washington.
But Brett Bruen, a former diplomat and advisor to president Barack Obama, says Biden is distracted by "Trump, guns and abortions".
Biden "appears content to get a few photos showing his strong leadership on the world stage and return home to focus on the fight for Congress in the fall."
James Carafano, a foreign policy expert at the conservative Heritage Foundation, is even more dismissive.
While the United States remains a leader, Biden's domestic record is "demonstrating that the possibility of American decline is real," he said.
"Our allies and partners, not to mention our adversaries, are acting accordingly. Many of them are already starting to prepare for the post-Biden era."