The relevance of NATO as a military alliance has been questioned repeatedly since the collapse of the Soviet Union in 1991.
With its prime mandate seemingly gone, NATO continued with peripheral roles in the Balkans, Afghanistan, Libya and elsewhere, but its plans for deterring Soviet aggression in western Europe quickly gathered dust.
That all changed, however, when Russia annexed Crimea through a bogus referendum and deployed troops on Ukraine's border.
NATO has responded by dispatching fighter jets to Poland, Romania and the Baltic countries, cancelling military co-operation with Russia and announcing plans for military co-operation with Ukraine.
Suddenly, NATO seems relevant again, even though every western leader has said diplomacy is the only way to resolve the crisis. Even the possibility of a Russian incursion into eastern Ukraine would not trigger a military response, although it would bring down heavier sanctions.
Some of the former Soviet republics that are members of NATO have welcomed the idea of a reinvigorated military alliance, but it's unclear how countries like Belgium and the Netherlands might feel about the obligations and risks they would face in the unlikely event of Russian military aggression against a NATO member.
In 1949, NATO was composed of just 12 members who shared a common interest, but the alliance today is made up of 28 members with differing views on how to respond to the Russian bear.
Everyone agrees the crisis must end at some time, even if Crimea remains in Russian hands, but relations are likely to be chilly for many years.
NATO's importance may be questioned yet again in the future, but for now, a revitalized military alliance is both prudent and necessary.