Profile: Who Is New NATO Chief Jens Stoltenberg?

Jens Stoltenberg has been an advocate of maintaining good relations with Russia, though he described its use of military force in Ukraine as "unacceptable."

NATO has named Norway's former Prime Minister Jens Stoltenberg as its next civilian head, starting on October 1.

Stoltenberg's appointment on March 28 as NATO's 13th secretary-general comes at a delicate time for the alliance. Russia's annexation of the Crimean Peninsula has heightened tension between the West and Moscow, and NATO is preparing to withdraw most its forces from Afghanistan by the end of the year.

But who is the 55-year-old career politician, the first Norwegian to occupy NATO's top post?

His ability to form consensus across party lines has often been cited, as well as his cross-border negotiation skills.

The son of a former defense and foreign minister, he lived for several years as a child in Belgrade, where he learned to speak Serbian.

As a teenager in the 1970s, Stoltenberg admitted to having thrown rocks at the U.S. Embassy to protest against the Vietnam War.

When he led the Labor Party's youth wing in 1985, he first affirmed the platform's position that Norway's should leave NATO, but later pushed the group to change its position. He eventually became the head of Norway's Labor Party.

An economist by training, he served in the 1990s as finance and trade minister, advocating for the country to save up its vast oil wealth for more difficult times. In 1995, he joined a bicycle rally from Oslo to Paris to protest nuclear-weapons testing by France.

Stoltenberg has served for more than 20 years in parliament and held the post of prime minister for a decade, from 2005 to 2013.

During his premiership, the Scandinavian country contributed troops to NATO's military mission in Afghanistan and aircraft to patrol a NATO-led no-fly zone over Libya.

In June 2013, Norway's foreign minister announced that the government had secretly brokered peace talks between Taliban and the Afghan government, paving the way for direct negotiations between the warring parties.

Cooperation With Moscow, To A Point

Stoltenberg has also been an advocate of maintaining good relations with Russia.

He negotiated a treaty with Moscow to end a bitter 40-year dispute over the two neighbors' maritime borders. The deal, signed in 2010, allows for new oil and gas exploration in the Arctic region. Stoltenberg is also reported to have built a personal friendship with then-President Dmitry Medvedev.

At the 2010 NATO summit in Lisbon, Stoltenberg called for cooperation with Moscow, saying, "We will make a fresh start in our relations with Russia, with the aim of building a strategic partnership." He said the alliance and Russia were facing many common security challenges, which "can best be addressed through cooperation, for example in the NATO–Russian Council."

Recently, however, he has made it clear that Russia's use of military force in Ukraine is "unacceptable." "Russia's move is in breach of international law and it's a type of power policy that belongs in a past era," Stoltenberg said. "We will not live in a world where the strongest one prevails," he added.

Stoltenberg shot to prominence on the international stage after far-right fanatic Anders Behring Breivik killed 77 people over the Labor Party's support for immigration in July 2011.

At the memorial service for the victims, Stoltenberg pledged to combat the atrocity with "more democracy, more openness, and more humanity, but never naivety." He reiterated his message at a wreath-laying ceremony marking the first anniversary of the attacks:

"The bombing and the shooting were meant to change Norway but the Norwegian people answered by embracing our values," he said. "The perpetrator failed -- the people won. Today we remember the 77 who were killed, eight of them here in the government quarters."

In December 2013, UN Secretary-General Ban Ki-moon named him a special envoy on climate change to mobilize political will to forge a new international climate deal.

Stoltenberg's appointment as NATO's secretary-general was not a surprise, as he was reported to have the support of the four most powerful NATO countries -- United States, Germany, Britain, and France.

But some have questioned NATO's choice.

In an editorial published in "The Wall Street Journal Europe" this week, Sohrab Ahmari said: "Before entrusting their alliance to his care, NATO members should inquire into Mr. Stoltenberg's current views on America's partnership with Europe, on the Russian threat and on nuclear weapons, which form a pillar of NATO deterrence. As it is, his public record suggests a mind ill-suited to the job."