In 1941 in order to compensate for the relative poor box office of "Pinocchio" and "Fantasia", Disney produced a low-budget feature film, "Dumbo". Just a few days after rough animation was complete on "Dumbo", the Disney animators' strike broke out. This was caused by the Screen Cartoonist's Guild (which had been formed in 1938), who severed many ties between Walt Disney and his staff, while encouraging many members of the Disney studio to leave and seek greener pastures. Later that year, "Dumbo" became a big success, the first for Disney since "Snow White". The critically acclaimed film brought in much-needed revenue and kept the studio afloat. A few months after "Dumbo" was released in 1941, the United States entered the war after the attack on Pearl Harbor. This led to the mobilization of all movie studios (including their cartoon divisions) to produce propaganda material to bolster public confidence and encourage support for the war effort.