Why the indefinite article in "Their campaign mounts in fury as a free Europe crumbles"

From The Imitation Game (2014), more spefically, from a WW2-era newsreel snippet inserted into the movie to keep the viewer up to date with the events:

"The German Army has fanned out across Europe, From Poland to Serbia, Lithuania to Denmark, Norway to France. The Nazi flag now flies from more than two dozen national capitals. Their campaign mounts in fury as a free Europe crumbles". (The newsreel is in an "old newscaster voice", clearly framed as contemporary with the events; there is some black-and-white historical footage being shown while this voice pronounces the words.)

Why a free Europe and not the free Europe? Everybody knew what the word Europe meant, and everybody knew what the free Europe was: it was the part of Europe not under the Nazi rule. Why introduce it all over again with the indefinite article?

I feel that the indefinite article might be okay here, but I would like to be able to explain this usage to someone else.

Maybe we could read the sentence as a shortening of

Their campaign mounts in fury as the part of Europe that is a free Europe crumbles. ("partitive use" of the indefinite article?)

Answer

This use of the indefinite article, especially in combination with the historical present (or reportage-present), often occurs in narratives as a scene-setting device. Consider:

A young Pele wakes up at the age of 9 and decides to become a saxophonist not a football player.

Grammatically, I think you're onto something when you suggest a partitive use but not as "that part of Europe which is free", rather on a more abstract level. If we imagine the noun as belonging to a set of versions of itself:

{young Pele, Pele in his prime, Pele in middle age, older Pele}
{free Europe, Europe under the looming threat of Nazi occupation, Europe of countries many of which are now Nazi-occupied}

then the indefinite article plays a selective function. From among these versions, that one. This function can also underlie the use in hypothetical contexts:

Imagine a world without hunger.

{world with hunger, world without hunger}