From The Making of Casablanca: Bogart, Bergman, and World War II:
[During shooting] Bogart was snappish and moody. Love scenes were uncharted waters for him. “I’ve always gotten out of my scrapes in front of the camera with a handy little black automatic,” he told a journalist who visited the Casablanca set during production. “It’s a lead pipe cinch. But this. Well, this leaves me a bit baffled.” The interview is typically frothy and insubstantial as Bogart plays with the idea of becoming a sophisticated lover or a caveman lover. But, even as he jokes about it, his uneasiness is obvious. “I’m not up on this love stuff and don’t know just what to do.”
According to a memoir by Bogart’s friend Bathaniel Benchley, before Casablanca began shooting, a mutal friend, Mel Baker, advised Bogart to stand still and make Bergman come to him in the love scenees. Bogart appears to have taken the advice, but his reticence may have been as much innate as calculated. Nearly a dozen years after Casablanca, Bogart told a biographer that love scenes still embarrassed him. “I have a personal phobia maybe because I don’t do it very well,” he said.
“What the women liked about Bogey, I think,” said Bette Davis, “was that when he did love scenes he held back — like many men do — and they understood that.” Miscast as an Irish horse trainer in Dark Victory, Bogart had tried to make love to Davis, who played his rich employer. Said Davis, “Up until Betty Bacall I think Bogey was really embarrassed doing love scenes, and that came over as a certain reticence. With her he let go, and it was great. She matched his insolence.”
However distant Bogart and Bergman may have been from each other in real life, and however uneasy Bogart may have been with Bergman in his arms, their love scenes have the poignancy and passion that Hollywood calls chemistry. “I honestly can’t explain it,” says Pauline Kael, “but Bogart had that particular chemistry with ladylike women. He had it with Katherine Hepburn in The African Queen and he so conspicuously had it with Lauren Bacall — who pretended to be a tough girl but really wasn’t — in To Have and Have Not. But he didn’t have it with floozy-type girls.”
Critic Stanley Kauffmann explains the match between Bogart and Bergman as the resonance of a relationship between brash America and cultured Europe. “She was like a rose,” he says. “You could almost smell the fragrance of her in the picture, and you could feel his whiskers when you looked at the screen. It was intangible.”