The Sand Pebbles (1966) on Netflix

In 1926, U.S. naval engineer Jake Holman is assigned to the gun boat U.S.S. San Pablo - nicknamed the Sand Pebble - this being the latest in a very long string of assignments due to a unyielding view of his work leading to conflicts with many of his colleagues and ship captains. Life on the Sand Pebble is no different. The Sand Pebble is patrolling the interior waters of China, where the the U.S. government is trying to protect its interests in the face of Nationalist and Communist battles against the feudal warlords. On board the Sand Pebble, Holman must deal with a captain whose wants often do not match what Holman can carry out. Ultimately the Sand Pebble is placed under quiet siege by the Chinese who are using this action as a symbol of the unwanted U.S. presence. Holman is implicated in an incident which could cause the start of an "all out" war, and as such places him in a bad position with his shipmates. Amidst all this turmoil, two romances occur, the first between Holman's colleague, good-hearted Frenchy Burgoyne and a slave girl named Maily, and the second between Holman and missionary schoolteacher, Shirley Eckert. Both romances face major obstacles.