John Wayne and Patricia Neal star and Ward Bond and Philip Carey play supporting roles.

The technical advisor was World War II Admiral Charles A. Lockwood, Commander, Submarine Forces, Pacific (COMSUBPAC).

During World War II, the submarine USS Thunderfish, under the command of Commander John T. "Pop" Perry, while on a special mission to the Philippines, is charged with rescuing a group of nuns and children, including a newborn infant nicknamed "Butch", and transporting them to Pearl Harbor.

Her superior, Commander Steele, overhears the conversation and castigates Mary for throwing away her chance for happiness with Duke.

Once Pearl Harbor acknowledges the message, Duke salvoes his torpedoes and makes a run for it, throwing the attacking Japanese warships into chaos.

Thunderfish, now assigned to lifeguard duty, helps to rescue shot-down American flyers, and does so while under attack from Japanese fighters.

Nearly fourteen years later, however, they worked together on In Harm's Way (1965) where she noted that he had mellowed a lot, possibly because he was seriously ill with lung cancer at the time.

The film's opening foreword and dedication states: "When the Pacific Fleet was destroyed by the Japanese sneak attack on Pearl Harbor, it remained for the submarines to carry the war to the enemy.

The special mission shown at the beginning of the movie, in which Navy submarines ran war supplies into the Philippines and evacuated civilians, while idealized is a matter of historic record.

A poorly designed and tested firing pin could malfunction on a good hit (that is, a torpedo striking within about 45 degrees of perpendicular to the side of the target).

The ramming and sinking of the armed freighter depicted in the scene occurred in the same action, just prior to Gilmore's death.

Two previous Warner Brothers features are cited within this film: George Washington Slept Here (1942) is traded to another submarine in exchange for Destination Tokyo (1943), of which a few seconds of footage is seen as the crewmen watch it.

USS Corvina (SS-226) was commissioned on August 6, 1943, and was torpedoed and sunk by the Japanese submarine I-176 on her first war patrol south of Truk Atoll on November 16, 1943.