Former Prime Minister and UN climate change envoy Jens Stoltenberg will become North Atlantic Treaty Organisation secretary general in October, at a delicate time for the security group after Russia's annexation of Ukraine's Crimea region.
Frank Aarebrot, professor of comparative politics at the University of Bergen and an acquaintance of Mr Stoltenberg, said: "If the task for Nato now is to defuse the crisis with Russia over Ukraine, then Stoltenberg will be eminent. He thrives on compromise. If the task is escalation he won't be bad, but there are others who could do a better job.
"He has a strong presence, in a Bill Clinton sort of way. When he's talking to you, you feel like the most important person in the world."
The son of a former defence and foreign minister, Mr Stoltenberg, 55, negotiated a deal with Russia that ended a four-decade dispute over their Arctic maritime borders and built a personal friendship with then-president Dmitry Medvedev.
He has made it clear that the annexation of Crimea by Russia, which has raised the need for Nato to boost its presence on Europe's eastern edge, cannot stand.
He said: "Russia's move is in breach of international law and it's a type of power policy that belongs in a past era."
Mr Stoltenberg, who lived for several years as a child in Belgrade where he learned to speak Serbian, served 22 years in parliament and was Prime Minister from 2005 to 2013 at the head of a Labour Party-led coalition.
Jan Egeland, a former UN Under-Secretary General, said: "His strength is that he's got a vast political network and good political intuition, and he will also listen to civil society, not just people within the 'security cage'.
Mr Stoltenberg pushed his government to mediate, often in secret, to resolve some of the world's longest conflicts, hoping Nordic patience and long history of mediation would bear fruit.
Norway's diplomats helped bring Colombia's government and Marxist FARC rebels to the negotiating table in 2012 and mediated between the Taliban and the West, once even bringing Taliban leaders to Oslo to engage them on democratic rule.
He started in politics early and admitted to having thrown rocks at the US embassy as a teenager in the 1970s, protesting against the Vietnam war.
When he took over leading the Labour Party's youth wing in 1985, he initially affirmed the platform's position that Norway's should leave Nato but eventually pushed the group to reverse its position.
He served both as finance and trade minister in the 1990s, advocating that Norway should save up its oil wealth for a rainy day, and during the financial crisis he used the cash to spend the country out of the crisis.
As Prime Minister, he also backed Nato's military campaigns in Afghanistan and Libya.
Many outside Norway know him best for consoling his nation and advising against hate-driven reactions after far-right gunman Anders Behring Breivik killed 77 people, mostly teenagers, over Labour's support for immigration in 2011.."