This documentary style presentation of the underground activity of the OSS in France in WWII claims to be factual. There is the typical stentorious voice over which implies authenticity. And there's a title card claiming it was all shot on the locations of the actual events. But this isn't true, it was extensively filmed in Canada.
And what began life as a biopic of a leading espionage official in Washington was compromised when he took his name off the project. As the story progresses, the narrative gets less credible. So this is a Hollywood spy thriller, and it's successful on those terms. There had actually already been a film about US intelligence a year earlier, called OSS.
The neorealist style is one Henry Hathaway adopted across many genres in the late '40s. James Cagney leads the espionage unit and shows us plenty of his apparently genuine combat skills. Annabella brings some authentic Frenchness, though unfortunately hardly figures. And one of the support cast turns out to be a Nazi counteragent...
What starts as a procedural presentation of training and operations evolves into a pro-American blockbuster. And both parts work fine. The realism is interesting and the climax is exciting. Though admittedly it's a shameful deception to claim this is all non-fiction. And the title, that's the location of gestapo HQ in Le Havre. Or so they say.