Stoltenberg, NATO's 13th secretary-general, took over in 2014 - the year "little green men" from Russia infiltrated Ukraine.Â
Moscow annexed the Crimean Peninsula, sparking a defence spending build-up at the world's biggest security alliance that gathered pace during his term.
�� Secretary General — NATO (@NATO) @jensstoltenberg reflects on the future of NATO and shares the personal motivations that led him to accept the job, and how his parents' values and his own political activity as a young man shaped his views of NATO ↓September 30, 2024
His tenure was surpassed only by Dutch diplomat Joseph Luns who spent 12 years in charge of NATO.
On Tuesday, a series of events to mark the handover will be held at NATO headquarters in Brussels, Belgium.Â
NATO secretaries-general run the headquarters, drive the alliance's working agenda and speak on behalf of the 32-nation organisation with one unifying voice.Â
Continuity is usually the keyword when they take up office.
Rutte becomes NATO's top civilian official as Russia's full-scale invasion of Ukraine approaches the 1000-day mark.
Political uncertainty within the organisation is also high, as election fever roils the United States, its unofficial "chairman of the board" and most powerful member.
Russian forces are making advances in eastern Ukraine.Â
NATO's ranks have swelled to 32 countries since Russia invaded Ukraine. (AP PHOTO)
Ukraine's army has a shaky hold on part of the Kursk region in Russia, which has provided a temporary morale boost, but as casualties mount it remains outmanned and outgunned.
Rutte will have to find new ways to encourage support for Ukraine among the allies, whose ranks have swelled to 32 countries since the invasion as Finland and Sweden joined to seek protection from Russia under NATO's security umbrella.
Across the Atlantic, surveys suggest the US election in November will be a close race.Â
It could deliver the White House to Donald Trump, whose bluster during his last term of office about low defence spending among European allies and Canada undermined the trust of NATO member countries.
It became an existential challenge, as smaller members feared that the US under Trump would renege on NATO's security pledge that all countries must rescue any ally in trouble - the foundation stone the alliance is built on.
Trump has been critical of US aid to Ukraine and suggested last week that President Volodymyr Zelenskiy should have made concessions to Russian leader Vladimir Putin before he launched his invasion in 2022.
