North Korea fired another missile yesterday, making it at least 20 in 11 different tests since it broke a test freeze in May. The launch is worrying in itself but the motivations and wider global security environment point to the many dangers ahead between now and Nov 3, 2020, when the United States holds its next presidential election. The US is being tested, and not just by Pyongyang, which timed the missile test with the announcement that it was resuming talks with the US on its nuclear arms programme. Just a day earlier, Beijing paraded a new missile, the Dongfeng-41, to mark the 70th anniversary of Chinese Communist Party rule. It is believed to be the world’s longest-range intercontinental weapon, capable of reaching the US in 30 minutes and designed to bypass its anti-ballistic missile system. Just a few weeks before that, on Sept 14, world oil markets were rocked when oil facilities in Saudi Arabia, a strong US ally, were hit by drone and missile strikes. Iran has denied it was behind the attacks but clearly tensions in the Middle East are rising, with the US also blaming Teheran for attacks on several oil tankers in the Gulf. Each of these challenges is arguably not surprising.

Foreign policy crises for the US come with the territory as it were. But what makes things especially worrying is that they come amid a new challenge: impeachment proceedings just beginning against President Donald Trump. Unlike previous moves against presidents Richard Nixon and Bill Clinton, this is happening in an America that is more intensely divided. The bitter partisanship is fuelled by social media, which did not exist previously, and not least by a combative President who thrives on Twitter wars. In 1974 when the House Judiciary Committee voted articles of impeachment against Mr Nixon, six of its 17 Republicans joined the Democrats in approving them. Mr Nixon quit, largely because leading Republicans publicly warned him that most members of his own party would not back him in a Senate trial. A Gallup poll before the House vote on Mr Clinton showed 26 per cent of Republicans opposed to removing him from office. By contrast, a recent survey found a stark divide: 95 per cent of Democrats supported an impeachment inquiry against Mr Trump; 91 per cent of Republicans opposed it.