"I think he just got mad," said Judith Morgan, coauthor of the book Dr. Seuss and Mr. Geisel. "He saw the growing threat in Europe and thought the Americans were not paying attention."

His outrage may have had something to do with his background. German was spoken in his childhood home, and between the two wars he traveled and studied in Europe. His intimate knowledge of the continent, combined with his left-leaning politics, made Nazism especially horrifying to him. "I think he was also teased for his German heritage as a child," Morgan said. "So he may have wanted to prove how strongly he felt about America."

In Geisel's political cartoons, Hitler showed up as a villain in many forms: a mad scientist amputating limbs, a bureaucrat giving orders to the devil, a trophy hunter trying to add a Russian bear to his taxidermy collection. In contrast, Mussolini was depicted as a bumbling idiot. In one of Geisel's cartoons, the Italian dictator furiously pedals a motorbike with tank treads. "Yoo hoo, Adolf!" he calls out in the direction of Russia. "Lookee! I'm attacking 'em, too!" But his bike is tied to a post.

Later in life, Geisel admitted that many of his political cartoons were "hurriedly and embarrassingly drawn" and "full of many snap judgments." That was never more true than when he focused on the Japanese. Instead of mocking their leader, as he did with Germany and Italy, Geisel ridiculed the Japanese people, drawing them as grinning menaces, stray cats, and slithering worms.

He even took on Japanese Americans -- a puzzling move for a grandchild of four German immigrants. One of Geisel's cartoons shows a cheerful line of slant-eyed people marching down the West Coast, picking up blocks of TNT and looking out over the Pacific for a "signal from home." It appeared in print on February 13, 1942, just six days before Franklin D. Roosevelt signed the order that sent more than 110,000 Japanese Americans to internment camps.

According to Morgan -- who was Geisel's close friend as well as his biographer -- the artist later regretted some of his cartoons, but he remained proud of others. "He specifically liked one about racial harmony, which shows an organ that has cobwebs forming over the black keys for lack of use," said Morgan. "That was the kind of cartoon that had lasting value."

Another of Geisel's lifelong favorites showed a matronly woman reading a book called Adolf the Wolf. "'And the Wolf chewed up the children and spit out their bones,'" the woman reads to the two horrified-looking children, before adding, "but those were Foreign Children and it didn't really matter."

Geisel had the same mixed feelings about his political work with Frank Capra. Toward the end of the war, he worked with the Hollywood director to write a number of short films for the U.S. government. He told Morgan that some of them had turned out more militant and vitriolic than he would have liked. "You'll see flowers; you'll see some mighty pretty scenery," the narrator intones in a 10-minute film instructing American soldiers on how to behave in occupied Germany. "Don't let it fool you. You are an enemy country. Be alert, suspicious of everyone."