The process was described by senior US and European officials.

Instead, a set of marathon meetings, a strategically timed phone call from Biden to Erdoğan and a last-minute shutdown resulted in the road being cleared for NATO’s newest members. In the end, Biden dangled with the prospect of a formal meeting with Erdoğan in the margins of this week’s summit when he pressed to get the pitch over the finish line.

Following Russia’s invasion of Ukraine, it is clear why Finland and Sweden would consider abandoning their long-standing security positions to join NATO. But in December, before Russian tanks began rolling into Ukraine, the outlook was far-reaching.

Still, on December 13, Biden made a phone call to Niinistö to raise the idea. Russian President Vladimir Putin had gathered troops and equipment along Ukraine’s borders. And it was clear to him that the security situation in Europe was about to change dramatically.

In March, after the invasion began, Biden invited Niinistö to the White House for talks. The two men sat in the oval office and found out details about the proposal, and they picked up the phone and called Andersson in Sweden – where it was after dark – to fill her in.

In May, the two countries formally submitted their applications to join the NATO alliance. The next day they were in the White House rose garden with Biden marking a historic milestone.

“After 200 years of military freedom of alliance, Sweden has chosen a new path,” Andersson said.

“Finland has made its decision after a quick but very thorough process,” Niinistö added.

However, clouding the celebration of the Rose Garden was a strong opposition from Turkey to adding new members to the alliance. By far NATO’s most challenging member, Erdoğan accused the nations of harboring members of the separatist militant Kurdistan Workers’ Party, also known as the PKK, which Turkey sees as a terrorist organization.

He also wanted the countries to get rid of an embargo on arms sales to Turkey that was imposed after Turkey’s military intervention in northern Syria in 2019.

The three countries continued to talk. But in a conscious decision, Biden tried to keep his distance and avoid putting the United States in the middle. Instead, Biden chose his moments selectively to try to help put his thumb on the scale to get this over the finish line, according to a senior administration official.

“The Americans do not want to sit in the middle of this because the price will then go up,” said a European official. “If the American (president) somehow indicates that this is the problem, (Erdoğan) will have a whole lot of other things he wants to ask for.”

Nevertheless, talks between the various parties continued. National Security Adviser Jake Sullivan and Foreign Minister Antony Blinken spoke with their Turkish counterparts. Finland and Sweden maintained their own talks with Turkey. And the conversations continued.

As the Madrid summit approached, US and European officials became increasingly frustrated with Turkey’s opposition, which some believed was being carried out with the intention of obtaining concessions. Officials who once privately said they hoped the Madrid summit would serve as a welcoming party for the alliance’s two newest members came to believe the prospect was unlikely.

“I am not sitting here today proposing that all issues be resolved by Madrid,” Sullivan said on Monday – a day before Biden’s arrival in Madrid.

But as the summit approached, there were signs of progress. And on Tuesday morning, Biden received a request from Niinistö and Andersson: It was time for him to call Erdoğan.

Speaking from the Bavarian Alps, where he attended the G7 summit, Biden encouraged the hitherto reluctant Turkish leader to “seize the moment and get this done in Madrid,” the administration official said. And he told him that if the agreement could be reached before the summit began, it would set the stage for a formal bilateral meeting between the two men in Spain.

“It is Turkey’s standard practice not to make concessions until the last possible moment. And the last possible moment is usually defined as a bilateral one with the President of the United States,” the European official said.

The strategy proved effective. Early in the evening, Niinistö, Andersson and Erdoğan announced that Turkey’s objections had been dropped and that Finland’s and Sweden’s applications to join NATO would proceed. And Biden will formally meet Erdoğan on Wednesday.

Turkey said it “got what it wanted” in the agreement, including cooperation on “extradition of terrorist offenders”. The senior US administration official said there were “a bunch of moving parts” and not a “single word or phrase” that proved the last problem.

Erdoğan’s long-standing complaints against the United States, including Washington’s refusal to sell Turkey’s F-16 fighter jets and his demand that the United States extradite a priest he accuses of cultivating a coup attempt, remain unresolved – and are likely to arise in his meeting with Biden.

Whatever the dispute once was, the leaders framed the result as a triumph. And more than four months into the Russian war in Ukraine, NATO is ready to welcome two new members.

“Congratulations to Finland, Sweden and Turkey on signing a trilateral memorandum – a crucial step towards a NATO invitation to Finland and Sweden, which will strengthen our alliance and strengthen our collective security – and a great way to start the summit.” wrote Biden on Twitter.

The picture was from their meeting in May when they entered the Rose Garden.