A Canadian tank arrived in Poland on Monday, and will head off to bolster Ukrainian efforts agains a Russian invasion. The single tank, obviously, isn't critical on its own, but what it represents definitely is: It's a German tank, which Canada could not have offered without German agreement, which shouldn't be taken for granted.Nearly a year after the war started, holding NATO's supportive alliance together is paramount, and these tanks are a symbol that it remains. They are also critical because as the territory warms up, Russia is likely planning new incursions—and the tanks will allow Ukrainian forces to bring the fight to them. After nearly a year of death and resistance, and a cold, slow winter, what happens when the thaw arrives?GUEST: Matt Gurney, reporter and columnist, writing in The Line