A Boy a Girl and a Dog (1946)

During World War II a young boy and girl living with their respective families in an apartment house that had restrictions against pets adopt a lost dog and hide it in a vacant apartment which may have been the only vacant apartment in the United States at the time this movie was being filmed A burglar breaks in and the apartment is damaged when the dog and crook have a tussle This blows the dogs cover but the kids enlist him in the K9 Corps and the dog distinguishes himself in the WWII Italian campaign