WW2 spy movie and the Nazi hunt for the secret radios used by the Allies, late 1930s to early 1940s.

This is a World War 2 based spy movie with agents using a secret radio to aid the Allies.

The theme of the movie was about the Nazi hunt for these secret radios.

The movie is from the late 1930s to early 1940s while WW2 was still active. Black and White.

Possibly set in Nazi occupied France.

During the nighttime scene at the end of the movie a voiceover spoke about the heroes who gave their lives (one of spies had just been killed by the Nazis) in service to their cause/country. And I recall a panel truck driving away down a dark road.