Rhett Butler is a giant coward.
Now, some of you are probably saying, "Shmoop! You did not read the book closely enough! Rhett isn't a coward! He fights in the war and everything!"
And indeed he does. The folks who call Rhett a coward in the book generally call him one because they think he avoided combat in the war. Which is false. Rhett starts off the war as a blockade runner (which takes some courage, even if he insists it doesn't), but at the siege of Atlanta he decides to go off and join the army. His commanding officer later praises him as "A born artilleryman, a brave soldier, and an uncompromising gentleman" (52.110). Yup, dude brings the brawn.
For that matter, Rhett shows physical courage throughout the novel. He helps Scarlett escape from Atlanta during the siege, for instance, and after he murders a black man, he faces his sentence of death by hanging with seeming equanimity. There's really no doubt he has physical courage.
So, if he fought in the war, and he's willing to face death, why call him a coward?
Simple. We call Rhett a coward because he's afraid to tell his own wife he loves her. Rhett's afraid of Scarlett. And not just a little bit afraid. He's deathly afraid, shamefully afraid, and his fear ruins not only his life, but the life of those he claims he loves.
It can be a little difficult to see Rhett's cowardice here as cowardice, because the novel never quite presents it as such. For instance, at the siege of Atlanta, when Rhett is about to leave Scarlett to go into the army and perhaps die, he finally declares himself:
For I do love you, Scarlett, because we are so much alike, renegades, both of us, dear, and selfish rascals. (23.161)
This is supposed to be romantic and sweeping and exciting, perhaps. But what exactly is Scarlett supposed to do about it? She's exhausted and desperate after delivering Melanie's baby and she's trying to get out of the city; she can barely react at all—"she heard words, but they made not sense to her" (23.162)—and what she needs is support and help, not a declaration of love.
Cowardice makes Rhett selfish—which he recognizes (he calls himself "selfish"), but that doesn't make it any less unpleasant. He was too afraid to tell her before, and he only speaks now because he may die, which means he doesn't have to worry about the consequences. It's like he's a little boy shouting insults before scampering around the corner.
Even after Rhett and Scarlett marry, Rhett isn't willing to tell his wife what he feels. Instead, he wants her to make the first move.
Turning quickly, she frequently caught him watching her, an alert, eager, waiting look in his eyes.
"Why do you look at me like that?" she once asked irritably. "Like a cat at a mouse hole." (48.37-38)
Calling him a cat seems like it gives him too much credit; it's more like a beaten dog waiting to see if his master will throw him a bone. Again, this is his wife. He's married to her, but he's too terrified of her to admit that he cares about her, even though they live together and sleep together and have a child together.
He's so afraid, in fact, that when she's deathly ill after falling down the stairs, he doesn't go to her, but instead sits outside getting drunk, hoping that she'll call for him. She's delirious and sick and she needs him, and his terror is so overwhelming that instead of helping her, all he can think of is how he needs her to reassure him.
At the end of the book, Rhett flat out admits that his whole relationship with Scarlett is ruled by his preposterous and pitiful fear of rejection. He tells her:
I loved you but I couldn't let you know it. You're so brutal to those who love you, Scarlett. You take their love and hold it over their heads like a whip. (63.65)
And then again, a few lines later:
If you had only let me, I could have loved you as gently and as tenderly as ever a man loved a woman. But I couldn't let you know, for I knew you'd think me weak and try to use my love against me. (63.70)
Even as he admits his cowardice, though, he's unable or unwilling to accept responsibility. It's all Scarlett's fault for just being so darn mean; that's why he couldn't tell her. If he did, she might have demanded things from him; she might have used him (the fear of slavery and the whip slips in here like an ugly shadow). He even blames the fact that he slept with Belle on Scarlett, saying he did so because Scarlett was insufficiently "soothing" (63.70). Scarlett's demeanor, however, isn't exactly new news to Rhett by the time he makes his way to Belle's bed.
So again, Rhett says that Scarlett would have thought him weak and manipulated him if he told her he loved her. But part of love is being willing to admit that you are weak and needy. The person you love has power over you; that's part of what love's about. Rhett says Scarlett would see him as weak, but it really seems like it's Rhett himself who's afraid of weakness, Rhett himself who is so afraid of the woman he loves that he's willing to cheat on her and lie to her and treat her as a punching bag for his own insecurities.
At the end of the novel, Scarlett realizes she loves Rhett, and instantly goes to tell him—because she has a spine, and isn't going to spend four hundred pages wavering and whining like Rhett did. But when she tells Rhett, what does he say? He says that after being hurt by her before, and after losing Bonnie, he's simply too afraid to have a relationship with her. "I'll not risk my heart a third time" (63.79), he says, as if he ever were willing to risk it in the first place.
The book often presents Ashley and Rhett in opposition. Ashley is weak and vacillating, while Rhett is decisive and takes charge. Ashley is an incompetent dreamer; Rhett is a dashing doer. But in the end they're really more alike than not.
The last scene of the novel shows Rhett saying hard things about Scarlett—for instance, "It's a young age to have gained the whole world and lost your own soul, isn't it?" (63.85)—and while it seems like it's supposed to be an indictment of Scarlett, showing how unwomanly she's been and how her hard-headed single-mindedness has driven away the love of her life, upon closer examination, is it really Scarlett who's indicted?
It's Rhett, after all, who reveals that his whole life has, like Ashley's, been governed by his inability to act upon his love for Scarlett. It's Rhett who has behaved with consistent and merciless cruelty simply because, like Ashley, he has been too weak to own and acknowledge his own feelings.
Scarlett's tragedy, then, is not that she loved Ashley instead of Rhett. Rather, her tragedy is that she loved, in succession, two men who were afraid of her. "I can take care of myself, thank you!" (17.132), Scarlett tells Rhett, and rather than finding that attractive or admirable, Rhett immediately demurs: "Don't say that, Scarlett! Think of it, if you like, but never, never say it to a man" (17.134). She's stronger than him, and so he spends his life trembling and whining.
Maybe, after all, the novel does have a happy ending. Certainly, it would have been a bittersweet victory at best for Scarlett to spend the remainder of her days with Rhett, a brave man physically but a cowardly excuse of a husband.