After admitting last week that “we do not have a strategy yet” for dealing with the Islamist militants in Syria who have beheaded two Americans, Barack Obama has struck a more confident note on a trip to Europe this week.

The American president used a visit to Estonia on Wednesday to declare that the “defence of Tallinn and Riga and Vilnius is just as important as the defence of Berlin and Paris and London”. Yet at the opening of what has been billed as the most important Nato summit in decades, the uncomfortable reality is that Mr Obama is also struggling to develop a strategy for a Ukraine crisis exploding on Europes border.