Ketcham's professional cartooning career parallels that of his peer Charles Schulz: Ketcham enlisted in the Navy during WWII, after which he sold cartoons to a variety of popular magazines. He then created Dennis The Menace, which was first syndicated in 1951 (a year after Peanuts began).
Dennis began as a fairly conventional gag panel but in a short time both the humour and drawing attained a remarkable level of sophistication. (Surely the early widespread popularity of the winsome five-year-old rapscallion and his exasperated but infinity patient nuclear family had much to do with its timing at the height of the post-War baby boom.)
At their best, the Dennis gags were so visually inspired that they couldn't have existed in any other medium. The ideas behind even the best gags would not have been as pleasing if it weren't for the expressiveness of Ketcham's line, and his attention to facial nuance and body gesture, which provided exactly the degree of subtle and understated contrast to Dennis' notorious breaches of decorum.