Vivien Leigh is Scarlett O'Hara, a manipulative southern belle who gets tangled up with rogue Rhett Butler, played by Clark Gable. Their affair is carried out over the Civil War and the Reconstruction era as the two experience the highs and lows that come with wartime. Why it failed/how they broke up: Scarlett is in love with Ashley Wilkes, who goes on to marry his cousin. Rhett learns of her secret and promises to keep it and another man proposes to her before he enlists for the war. She marries him, then he's killed in battle. After Scarlett loses everything in the war, Rhett returns and offers to marry her; however, her heart still belongs to Ashley. The two have a very unhappy marriage that results in marital rape and the death of their child and Rhett's famous line "Frankly, my dear, I don't give a damn."
New Line Cinema