Ukraine knocks — again — on NATO's door. Who will answer?

When the subject of security guarantees and a pathway for Ukraine to join NATO was discussed at an informal function in Ottawa recently, one member of the diplomatic community started humming a few bars from an old Paul McCartney and Wings song.

"Someone's knockin' at the door. Someone's ringin' the bell. Do me favour? Open the door. Let 'em in."

The 1970s pop tune Let 'Em In is unlikely to become an ear worm for NATO leaders at the upcoming Vilnius Summit, but the sentiment is present and runs deep.

It has been 15 years since Ukraine was first nominated for membership in the Western military alliance by Canada under what's known as the "open door policy." 

A lot has happened since then. 

A major war on Ukrainian soil, marked by the bombing of its cities; the deaths of thousands of civilians and soldiers; the delivery and combat use of more NATO-standard equipment than most other alliance members hold in their inventories.

The war itself is related to the question of NATO membership: The Kremlin has used potential Ukrainian membership as a major argument in attempting to justify its invasion.

Outgoing NATO Secretary General Jens Stoltenberg routinely expresses confidence that Ukraine will join the alliance some day, once the war with Russia is concluded. All 31 leaders in NATO have publicly agreed. 

The government of President Volodymyr Zelenskyy formally asked to join last September.

Despite everything that's happened since the full Russian invasion in February 2022 and the seemingly united front among allies, the debate behind closed doors over when and how Ukraine should join is deeply divisive, with eastern European countries suggesting some major powers, including France and Germany, are against delivering firm timelines. 

It has, in fact, become a source of major tension over the last several weeks.

Prime Minister Justin Trudeau tried to put the best face on it when asked following his weekend meeting with Zelenskyy in Kyiv.

Ukraine's membership application was "very much a live conversation and Canada and many others are very supportive of Ukraine joining NATO when the conditions allow. What that exactly looks like is a conversation that we're continuing to have between now and Vilnius," Trudeau said.

"But I'm very positive about it."