What Bergman has got here is "What if all that bad stuff happened here in Sweden, to nice people like us?" And what he gives us, in the Swedish language, with Swedish actors, on Swedish locations (and using what appear to be genuine Swedish military vehicles) is what was familiar from war films set in almost every other country in Europe-- all the confusing invasions and counter-invasions, political lies, internment camps, faked confessions, summary executions, torture, turncoats, "collaborators", and so on. As in a modern short story, it's done in the abstract, with no real names, cities, or countries used. But the stronger faction are "Nazis": they strut about self-importantly, and some wear shiny knee boots. One even whips things with a riding crop (ok, it's actually a cane). The victimized couple are named Rosenberg. Apart from the shame they feel at finding dirtier ways to survive-- and who would not do what they did?-- what all of the above suggests is that the title is clearly meant to refer to Stockholm's de facto complicity with the Nazis. Indeed, what we are shown is what Sweden might have looked like if Germany had asked for a bit more than mining concessions.
The first half plays like a black comedy. We see the "fog of war" from the point of view of a comically passive couple who ignore the troops all around, the long convoys, the bombed-out buildings, the news reports, &c. They do not even bother to find a working radio. They are the ultimate in "Not in my backyard". They talk of wine and lingonberries; meanwhile friends are mysteriously conscripted and growing numbers of troops show up in the town. They show no curiosity about the war that has been going on around them for many years.
The man (Von Sydow) is cultured, sulky, and a navel-gazer; the woman (Ullman) is somewhat more impulsive, passionate, and outward-looking. There's a beautiful scene in which the man talks about his violin: the manufacturer, he says offhandedly, fought in the Napoleonic wars, but his own interest stops with the cultural artifact in his hand-- or, more precisely, which his own warm feelings about owning it, and the security that that ownership assumes. Not in my backyard! But when war finally breaks into their bucolic idyll, the man's timidity, an irritation in good times, turns into a liability, one he ends up overcompensating for-- as is often the case-- as Bergman demonstrates subtly and beautifully. Definitely worth seeing.