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?)