As Donald Trump’s cavalcade withdrew from Seoul, on Sunday afternoon in the steamy summer heat, you could almost feel the city exhale. There is nothing that disrupts normal life, even on a weekend, quite like the passage of a US president and his attendant officials, military and press corps — although the protests against Mr Trump’s presence had been small and there were others in support.
But the sting was still to come. Mr Trump upstaged his scheduled meeting with South Korea’s president, Moon Jae-in, with an impromptu encounter with North Korea’s leader, Kim Jong Un, in the demilitarised zone that divides the Korean Peninsula.
Procured by tweet, with none of the usual diplomatic preparation, the meeting brought a “will it or won’t it happen?” suspense to the day that consumed the news cycle. Then came Mr Trump’s showy 20 steps inside North Korea, the first taken by a US president in office into that enemy territory, followed by a summit of almost an hour (back on the South Korean side of the line) that aides would normally have spent months planning.
Yes, Mr Moon was a participant in those talks too. He has been a firm advocate of discussions with the North, and of anything — including Mr Trump’s unscripted diplomacy — that reduces tensions with the nuclear-armed neighbour. Mr Trump said, in remarks to US troops, that “President Moon will be there too,” in future talks with Mr Kim.
But Mr Trump’s courtship of North Korea and his casualness towards the US relationship with South Korea — warmth mixed with open questioning of the value of the alliance — is dangerous. His behaviour, whether out of design or lack of interest, calls into question an alliance that has been a cornerstone of American policy in the region for nearly 70 years.
The alliance goes back to 1950 when the US helped establish South Korea as a modern state and committed, under the 1953 Mutual Defence Treaty, to maintain a military presence there and help the country defend itself. There are currently around 28,000 American troops in the country, and South Korea contributes to the cost of supporting them.
Public opinion is more strongly pro-American than in many parts of the region; a 2017 opinion poll by the Asan Institute for Policy Studies found 96 per cent of South Koreans thinking the alliance “necessary”. However, Mr Trump has brought new strains. He has questioned whether the deployment is worth it for the US and pushed South Korea to pay more. The language he has used has suggested to his critics that he sees the arrangement only in terms of money. The exit of US defence secretary Jim Mattis, a firm defender of American alliances in the region, rattled many in Seoul.
In principle, Mr Trump’s overtures to North Korea, aimed at persuading Mr Kim to give up nuclear capability, suit the South. But his pursuit of this goal has been so unpredictable — from hurling insults such as “Little Rocket Man” by tweet to boasting of a beautiful friendship — that it hardly inspires a sense of security. Nor, his critics point out, has it secured firm results although tension has eased.
Meanwhile, Mr Trump has shown a lack of interest in how US allies in the region (including Japan) might be affected by his trade war with China. Analysts in Seoul point out the difficulty for South Korea if forced to pick sides. Yet Mr Trump has brought to the Chinese stand-off a vertiginous unpredictability, seeming this week to ease up on his opposition to US firms dealing with China’s technology company Huawei, a pivot that stunned many in Washington.
It would be wrong to say that relations between the US and South Korea are difficult — but they are cooler than they have been for many years. Mr Trump’s tactics towards the North may chime with Mr Moon’s. But he has injected a chill and a wariness into a relationship that was an unquestioned pillar of US foreign policy for decades. That may in turn embolden the North to resist pressure to change, undermining the course that Mr Trump says he is pursuing.
Mr Trump’s encounter with Mr Kim on the border generated the pictures he no doubt wanted the world to see. But he has not obviously changed the course of the enemy in the North, while doing little to ease the strains he has brought to the alliance in the South.
The writer is director of the Institute for Government, a think-tank