Jens Stoltenberg, a former prime minister of Norway, has been appointed to succeed Anders Fogh Rasmussen as NATO secretary-general, a post he will assume in October.
In an address in Oslo after he was selected by NATO ambassadors, Stoltenberg on Friday called the crisis over Ukraine "a brutal reminder of how important NATO is.
"I want to express my support that NATO does not accept the changing of borders by force within Europe," he said. "NATO has once again proven its relevance."
Rasmussen tweeted that Stoltenberg is "the right man to build on NATO's record of strength and success," and that "the Ukraine-Russia crisis shows [the] need for continued strong and determined leadership of NATO."
Rasmussen, a former Danish prime minister, has held the post as head of the 28-nation North Atlantic Treaty Organization since 2009.
U.S. Air Force Gen. Philip Breedlove, NATO's Supreme Allied Commander Europe, will remain the military head of the alliance, a position traditionally held by an American.
The Wall Street Journal notes that Stoltenberg "is well-known to NATO leaders from his nine years as premier of oil-rich Norway. He became known on the global stage in 2011, taking a very public role in helping his nation recover from a terror attack staged by Anders Behring Breivik, who claimed the lives of 77 people."
According to the Journal:
"Mr. Stoltenberg is known for his advocacy of causes like fighting global climate change rather than as a military leader. But he has a reputation as a strong NATO supporter during his time at Norway's helm, and is seen as a predictable, patient and pragmatic politician."
"Stoltenberg, 55, who was backed by the United States, Germany and Britain, will take over at a turning point in NATO's history.
"The urgency of the Ukraine crisis means that the alliance, which is due to end combat operations in Afghanistan at the end of this year, is likely to refocus back onto its core task of defending its member countries."
Italy's Franco Frattini, a former foreign minister, was also said to have been a strong candidate for the top post.