n July 2, a giant alien mothership enters orbit around Earth and deploys several dozen saucer-shaped "destroyer" spacecraft that quickly lay waste to major cities around the planet. On July 3, the United States conducts a coordinated counterattack that fails. On July 4 the a plan is devised to gain access to the interior of the alien mothership in space in order to plant a nuclear missile.

Overview from themoviedb.org