After being compelled to remain in Afghanistan when he wanted to withdraw, Mr Trump will redefine the battle as smashing terrorism in line with his supporters, even though he really will need to strengthen the Kabul government’s capacity to succeed.

Secretary of State John Kerry’s new diplomatic process for dealing with Syria’s harrowing civil war involves convening a series of talks in Vienna. The effort is probably well-intentioned. But I cannot conceive of what he expects to accomplish.

The upcoming Annenberg summit between Presidents Barack Obama of the US and Xi Jinping of China could define the strategic relationship between the two most powerful countries in the world for years to come. Mr Xi has called for a “new type of great power relationship”. Tom Donilon, the US national security adviser, has suggested a “new model of relations between an existing power and an emerging one”.