The Guardian view on Nato’s future: a reinvigorated alliance will need all its strength | Editorial

The summit in Lithuania has reaffirmed the organisation's newfound sense of purpose. But immense challenges lie ahead

Despite excitable speculation before the Vilnius summit, there was never a serious prospect that Ukraine could join Nato while it is at war - as Kyiv has acknowledged. Membership cannot be granted retrospectively amid a conflict. Article 5, which sets out the principle of collective defence - an attack on one is treated as an attack on all - works as a deterrent, not as a do-over.

Nor was there much prospect of this meeting even agreeing to a concrete timetable for membership afterwards. The alliance operates by consensus, but the US calls the tune because it pays two-thirds of the piper's wages. It has made clear repeatedly that it regards membership for Ukraine as a distant prospect.