This is the Prelude to 1941 Michael Powell, Emeric Pressburger wartime drama, "The 49th Parallel', here performed by the Shepton High School Full Orchestra of Plano, Texas. The film was not released in the USA until 1942 (under the title, 'The Invaders"). It won an Academy Award for Pressburger for
This prelude was composed by Ralph Vaughn Williams. The film follows a group of desperate German navy officers and men who, after their submarine is disabled after an attack in Hudson Bay, try to cross hundreds of kilometers to reach the Canadian border with the United States, hoping to be interned into a then-neutral United States. The film served as a propaganda drama about the contribution of Canadians to the war effort, and a none-too-subtle remainder to the Americans that the war in Europe was coming closer every day.
The Narration after the prelude sets one of the themes of the film---how in a world engulfed in war, two large nations live in peace with one another:
"I see a long, straight line athwart a continent. No chain of forts, or deep flowing river, or mountain range, but a line drawn by men upon a map, nearly a century ago, accepted with a handshake, and kept ever since. A boundary which divides two nations, yet marks their friendly meeting ground. The 49th parallel: the only undefended frontier in the world. "