Following a tremendous increase in UFO sightings worldwide and an attempt on the president's life, a black operations force designated the Extraterrestrial Combat Unit is activated by the CIA with the full support of the highest echelons of the federal government and the military. XCOM is tasked with investigating the extraterrestrial incursions and forming a counter to the invaders. They are our nation's first, and last line of defense. 

XCOM: UFO Defense