That’s the title of one of the great World War II propaganda posters, sometimes mistakenly referred to by the title "When you drive alone you drive with Hitler," which sounds better. That’s our modern idiom, and probably was back then too, but it’s evidently not what the government agency that produced the poster considered proper English. It’s fairly hilarious now, but some variation of it was used in other posters, and you can well imagine it must have worked.
Northwestern University has a collection of these propaganda posters available online, and while this poster apparently isn’t part of the collection, there are a lot of good ones there. I find these posters fascinating and many of them I find very moving, which is a testimony to how good they were, and are, as propaganda. Here are some from the collection.
I’ll leave you with one last poster, one of the most famous, that for some reason is not in the Northwestern collection.