Massey's the skipper, but the star is Humphrey Bogart, two steps away from gangsterism, and cracking wise. He's First Mate Rossi, whose "too easy-going to be a skipper," but given a chance could be a cracker-jack commander. Bacon sets up the rules and procedures for the vast convoy, but an attack in the mid-Atlantic separates the "Sea Witch" from the rest of the ships, and the rule-book goes overboard as the ship plays a cat-and-mouse game with a lone sub determined to sink it. While the flotilla attack is dependent on that unconvincing model-work, there's a later Luftwaffe attack on the ship that features amazing wire-work effects, not only on the planes maneuvering through the clouds, but also of bodies being blown from their stations when the ship takes a direct hit. There's no sugar-coating the dangers of war, but the difference between the sides seem to be that the Nazi's scream when they go their watery grave, while the Americans merely have their quips halted. Various strategies are employed to evade the sub, including "going quiet," thanks to the Scottish engine-man who will remind any watcher of a certain star-ship engineer willing to eke out "a wee bit more."
The action doesn't slacken as Bogart's Rossi makes a bold move setting the "Sea Witch" on fire to draw in the sub, and the film ends with a Rooseveltian declaration of solidarity (probably voiced by Stan Freberg), which would prove to be problematic in the 50's when McCarthy went after Hollywood. All in all, an interesting film for all sorts of historical reasons beyond the propaganda factor.
Bogart has a great speech about bravery mid-way through the flick that's worth noting:
"Let me tell ya something about my "iron nerve," son. It's made of rubber, just like everybody else's, so it'll stretch when you need
it. Ya know, people got a funny idea that being brave is not being
scared. I dunno, I always figured if ya weren't scared, there's nothin' to be brave about. The trick is...how much scarin' you can take?"