Lee Jae-myung had his eyes on South Korea's presidency long before winning a snap election on Tuesday.
After losing the last election in 2022, Mr Lee has finally taken power — but in a world where much has changed.
Mr Lee, who was promptly inaugurated on Wednesday, commenced formal duties as president at 6:21am local time.
An acting president had been in place after his predecessor Yoon Suk Yeol was impeached for declaring martial law.
The new president will immediately face an international stage vexed by hiked tariffs and trade uncertainty, US-China tensions, and growing ties between North Korea and Russia.
Observers of South Korea's politics say Mr Lee, who has been accused by opponents of being pro-China in the past, has already recast himself according to the new strategic landscape.
In his inaugural address on Wednesday, he vowed to restart dormant talks with North Korea and to bolster a trilateral partnership with the US and Japan.
But experts said Seoul's relationships with both Washington and Beijing would test Mr Lee's diplomatic agility.
Tariff talks await
US President Donald Trump announced 25 per cent tariffs on imports from South Korea, a country reliant on exports for its wealth, in April.
Along with neighbouring Japan, South Korea hopes to negotiate a lower rate and to shield its industries from the Trump administration's trade agenda.
University of Sydney Korean studies lecturer Su-kyoung Hwang said the country's strong relationship with the US would likely remain largely the same, and that Mr Lee "will likely reach out to Trump as soon as possible".
"Like every political leader on the planet right now, he needs to deal with Trump's capricious tariffs, the shifting international landscape, and an increasingly isolationist United States in the face of an ambitious China," she said.
While South Korean conservatives have leaned firmly pro-US, progressives like Mr Lee have historically advocated for more balanced relations, said the Australian National University's Korea Institute director Kyung Moon Hwang.
"Progressives are more open to engaging with China and North Korea," said Professor Hwang.
"But they still recognise the importance of the US security alliance ... [Mr Lee] has to try and find the middle ground."
The US, South Korea's strongest ally, has pushed for greater defence spending.
China, South Korea's largest trading partner, is important for dealing with North Korea.
"The China situation is interesting because it is economically crucial, but even more delicate because of the US administration," Professor Hwang said.
"It's a hard line to walk."
During his inauguration speech on Wednesday, Mr Lee didn't directly mention trade tensions with the US.
But he said he would prioritise revitalising a slowing domestic economy and immediately launch an emergency task force to wage a "head-on battle" against the threats of recession.
'Strategic ambivalence'
Mr Lee has stressed South Korea's alliance with the US remains the foundation of its foreign policy.
In the face of opponents accusing him of being pro-China and anti-American, Mr Lee has cast himself as a centrist and pragmatist on foreign policy said the ANU Korea Institute's Jay Song.
The adoption of a "strategic ambivalence" meant the new president would not take sides, Dr Song said.
"He will do the deal with the US when it's serving the [national] interest and he will also do, for example, trade ... with China."
And she said Mr Lee would likely be muted on tensions over China's claim on Taiwan — a matter that US Defense Secretary Pete Hegseth at the weekend claimed posed an "imminent threat" to the separately governed island.
In his inaugural address, Mr Lee promised to pursue "pragmatic diplomacy" with neighbouring countries and boost trilateral cooperation with the US and Japan.
"We will turn the crisis posed by the major shift in global economic and security landscapes into an opportunity to maximise our national interests," he said.
US Secretary of State Marco Rubio congratulated Mr Lee on his election on Wednesday.
"The United States and the Republic of Korea share an ironclad commitment to the alliance grounded in our Mutual Defence Treaty, shared values, and deep economic ties," Mr Rubio said.
Japanese Prime Minister Shigeru Ishiba said the importance of his country's ties with Seoul remained unchanged, calling for a bilateral summit as soon as possible.
Change to the North
Regarding North Korea, Mr Lee promised "strong deterrence" based on the US military alliance.
But he said he would "open a communication channel with North Korea" and establish peace on the Korean Peninsula "through talks and cooperation".
Dr Song said the victorious Democratic Party was known for being in favour of engagement with North Korea.
"But what they also realise is that North Korea's Kim Jong Un is not Kim Jong Un of let's say five or 10 years ago," she said.
"Kim Jong Un has changed. He already declared that he's not going to pursue any ... friendly policy with South Korea."
The new government would have to set its policy towards North Korea accordingly, she said, also considering the possibility that Mr Trump could push for a deal with Pyongyang.
"He may do something with North Korea directly, not involving South Korea even," Dr Song said.
"So [Mr Lee] and his foreign policy team has to calculate all these changes."
Yet any breakthrough remains uncertain.
North Korea's support for Russia's war in Ukraine, including the provision of troops and military aid to Moscow, has complicated international diplomacy with the West.
"The Ukraine situation really limits how far South Korea can go," Professor Hwang said.
ABC/Wires
