ObscureHollywood.net’s review published on Letterboxd :
Humphrey Bogart, an undercover Army officer, investigates the activities of pro-Japanese expatriate Sydney Greenstreet. Greenstreet and his Japanese associates are planning to blow up the Panama canal. Bogart wipes out the saboteurs and saves the canal. Mary Astor is around to provide a love interest while exchanging smart quips with Bogart.
Made less than a year after the bombing of Pearl Harbor, this film is a patriotic exercise in anti-Japanese propaganda. The cast includes many of the ethnic Asian actors seen in 30s and 40s films, including Keye Luke and Victor Sen Yung (Charlie Chan’s #1 and #2 sons respectively), and Richard Loo whose ability to project considerable menace led to his frequent casting as villainous Japanese during WWII.
Victor Sen Yung’s completely Americanized character is a US citizen (presumably) and, therefore, a traitor. The character plays into the suspicions, prevalent at the time, about the loyalty of Japanese Americans. These suspicions led to the internment of many Japanese citizens.