Occasionally, Snoopy will attack the cat "off-stage" if someone (such as Woodstock) is in mortal danger. However, Snoopy's attacks usually result in him looking beaten up or scratched when he reappears.
World War II's paw has been shown briefly in The Charlie Brown and Snoopy Show, in the short "Blanket" (in which Snoopy and Linus van Pelt try to retrieve Linus' security blanket from next door after Linus's friend Eudora gives it away to the cat) from the first season episode "Snoopy's Cat Fight" and in the short "Snoopy's Foot" from the second season episode "Snoopy and the Giant". His paw appears as orange in "Snoopy's Foot" but is white in "Blanket". Of course, it is possible for one cat to have paws of different colors.
Although never seen in the strip or in The Charlie Brown and Snoopy Show, it is likely that World War II is the same type of cat as Brutus from Race for Your Life, Charlie Brown and the cat that appeared in the TV special Someday You'll Find Her, Charlie Brown, given how vicious all three cats are toward the Peanuts gang in their appearances.