As the Russian invasion of Ukraine continues with no end in sight, NATO's much-celebrated unity faces fresh strains when leaders gather for their annual summit this week in Vilnius, Lithuania.
The world’s biggest security alliance is struggling to reach an agreement on admitting Sweden as its 32nd member. Military spending by member nations still lags behind longstanding goals. And an inability to compromise over who should serve as NATO’s next leader forced an extension of the current secretary general's term for an extra year.
