The leaders of Nato's 28 member-states met in Warsaw last week against a background of security crises on all sides. As the summit declaration put it, there is “an arc of insecurity and instability along Nato's periphery”.

One concrete and encouraging response to the varied challenges was a joint declaration by the NATO Secretary General and the Presidents of the European Council and the European Commission on giving new impetus and substance to the partnership between the EU and Nato. The two organisations agreed to co-operate in a number of areas, from countering hybrid warfare to improving maritime security.

The EU and NATO have both realised that the crises they face do not fit neatly into institutional boxes. Russia’s annexation of Crimea and invasion of eastern Ukraine demanded both sanctions, imposed by the EU, and military reassurance from Nato for allies in Central and Eastern Europe. Both organisations have something to contribute to solving the migrant crisis in the Mediterranean; to improving resilience in the face of cyber threats; and to making European defence industries more efficient. The joint declaration showed new pragmatism on the part of the EU, recognising that it is not in a competition for influence, but that “a stronger EU means a stronger NATO, and a stronger Nato means a stronger EU”, as Commission President Jean-Claude Juncker put it.