He has used all his experience after nearly two decades at the top table of world politics, honed in two stints as prime minister of Norway, to steer Nato through the rough seas it has faced under his leadership.
Nato’s world leaders underlined their faith in him by asking him to extend his eight-year tenure by another year after Russia’s attack on Ukraine. In so doing, Mr Stoltenberg, 63, gave up his long-held desire to become chairman of his native Norway’s central bank. The situation had given him "no choice" he said at the time, and felt it was the most important thing he could do with his life.
The reason why the US, French, German and British leaders asked him to continue was clear on Tuesday evening, as he calmly sat on a stool for 30 minutes being questioned over a range of issues at the Nato forum in Madrid.
He was asked about Turkey’s objection to Sweden and Finland joining the alliance. Turkey had “serious concerns on issues like terrorism”, he responded, being careful to pronounce the country’s newly-branded name “Türkiye” and acknowledging its issues with the Kurdish PKK terrorist-designated group.
He signed off by remarking that he was meeting the leaders of Turkey, Finland and Sweden, adding: “I hope that we can make some progress”.
Mr Stoltenberg calmly removed his earpiece and microphone and walked offstage. Beneath the unruffled exterior his mind would have been furiously working over the diplomatic language and guarantees required to reverse Ankara’s veto.
Four hours later, The National was among several media outlets to receive a memo from Finland’s presidential office stating that Turkey’s objections had gone.
Mr Stoltenberg learnt lessons in diplomacy from his father, a Norwegian foreign minister, and from his tenure as Norway’s prime minister when in 2011 right-wing extremist Anders Breivik planted a bomb outside his office, killing eight people, before going on to massacre a further 69 at an island youth camp.
His leadership following the country's worst peacetime attack was exemplary. He gave a dignified response at a memorial service for victims, pledging to combat the atrocity with “more democracy, more openness, and more humanity, but never naivety”.
Holding firm to Norwegian values resonated not only with his fellow countrymen but around the world. When the Nato position became free in 2014 he was duly selected.
It had been a journey from his left-wing teenage days, when he had thrown stones at the US Embassy in Oslo to protest against Vietnam bombings in the 1970s.
Later, as leader of Norway’s Labour Party youth wing, he initially supported its policy of exiting Nato, before persuading members to reverse and accept the alliance.
It was a trajectory similar to his political champion, Britain’s Tony Blair, whose more centrist politics of left-wing realism Mr Stoltenberg said had inspired him.
As Norway’s prime minister from 2005 to 2013 he sent troops to Nato’s mission in Afghanistan and war planes to the no-fly zone over Libya. He also helped broker peace talks between the Taliban and Afghan government in 2013.
More importantly for Norway, Mr Stoltenberg formed good relations with Russia, allowing the countries to conclude a treaty following a bitter 40-year Arctic maritime border dispute in 2010.
That relationship and tact may be critical if Ukraine war requires a negotiated peace, but it is Mr Stoltenberg’s avowal that Russia must be defeated and his outspoken demands for military aid to Ukraine, alongside increased Nato defence spending, that have given the alliance cohesion.
His legacy will be marked by Nato’s new Strategic Concept document to be published on Thursday.