The last and least memorable of John Ford's famous cavalry trilogy (following Fort Apache and She Wore a Yellow Ribbon), Rio Grande nonetheless has an interesting continuity about the gentlemanly rules of military conduct. Here the focus is on the family. While creating a heated controversy over his handling of the Apache war, John Wayne must also contend with disgruntled wife Maureen O'Hara and estranged son Claude Jarman Jr., a new recruit trying to earn his father's love and respect. Ford seems to suggest that there are two conflicting codes of honor in every cavalry officer's life, the personal as well as the professional, and that it takes an act of heroism to maintain both. It's fascinating to observe Wayne's progression throughout the trilogy, as his personal stakes intensify. Also, this is the first of five onscreen appearances between the Duke and O'Hara, each filled with a competitive spirit and stormy sexuality.