"The Mouse that Roared"  -   a great black and white movie from the 50's with Peter Sellers when a tiny country invaded the US and won.   Everyone was in the fallout shelters during a drill and they took over the government .   They invaded on the premise that countries the US went to war with and were  defeated were  given aid  after the war,  such as Japan and Germany,  and so they would be.   But they won!