The United Kingdom got its third prime minister in three years on Wednesday, when Boris Johnson defeated his rival Jeremy Hunt to become leader of the Conservative Party and finally realized his ambition of moving into No 10 Downing Street.

How long his sojourn will be remains to be seen — not least because his predecessor notably failed to find a way to accomplish Brexit and unite the country.

His brief victory speech was full of high-pitched optimism and grand ambitions. But he is unlikely to find the going any easier. Having adopted a hard-line "come what may" stance on the UK leaving the European Union, he now has to find a way to deliver on that, given that Parliament has already decided that a no-deal is not an option.

One after another foreign leader has congratulated him on his win, but most will be hoping he softens that stance and can navigate his way to some kind of accommodation with the EU to avoid the worst-case scenario of a no-deal Brexit, which would not only plunge the world's fifth-largest economy into a recession, but also be a black swan event setting off an undesirable chain reaction in the global economy.

However, so far, he has offered little to suggest that he has the ability to mobilize either Parliament or the EU, which insists it won't negotiate with the UK beyond the agreement reached with his predecessor Theresa May. If he cannot maneuver a new deal, or Parliament rejects whatever Johnson brings back from Brussels, Brexit is in danger of becoming akin to the is-it-isn't-it dead cat in the box.

At the same time, as well as appeasing Parliament somehow, he faces another delicate balancing act. He is buddy-buddy with the US president, and will obviously be hoping the US administration will come good on its promise of a quick and favorable trade deal should the UK unceremoniously sever its ties with the EU. Given that the United States has decided to lock horns with China on trade, tech and other issues, it is likely to make it a condition of any deal with the UK that it is precluded from having a free trade agreement with China And a FTA with China is something the UK has also pinned its hopes on post-Brexit.

So he is going to have a lot on his plate. In a divided country, to put smiles back on people's faces is one thing, to put confidence in their hearts about the future is another. In a divided world, instilling confidence that the UK can manage the mess of its making without dragging others into it will be even harder.