During the past centrury's two world wars, the U.S. government asked a lot from its citizens -- it asked for savings, for labor, for patriotism, and for sacrifice. And to ask for these directly, various departments of the federal government launched ad campaigns that urged -- sometimes scared -- people to contribute to the war effort. Some posters evoked images of the brutality of our foreign enemies, others suggested the American way of life was in jeopardy. Many of the ads were directed toward selling war bonds -- direct loans to the government. This sort of wartime propaganda has recently come back into the public imagination by way of the new Captain America movie, which shows super-soldier Steve Rogers, the Army not knowing what to do with him, being enlisted for a traveling show to promote war bonds.

These efforts were effective, too. According to the Ad Council, approximately 85 million people purchased U.S. war bonds in the 1940s.

Here's a look at some of the ad campaigns from both world wars, compiled from the Charles B. Burdick War Poster Collection at San José State University Library.