National Geographic: Alien Invasion: Weapon designers, military strategists and biologists reveal why it's crucial they prepare for an alien attack, and the plans they have drawn up for how humans would fight back

When Aliens Attack

What if an extra-terrestrial force attacked Earth? What might that look like and how will the people of Earth respond? Consulting a cast of world-renowned scientists, survival experts and defense experts, National Geographic explores this frightening scenario. Experts reveal what could motivate alien invaders to attack Earth, and speculate on how the attack might play out, the strategy alien invaders might use, and the most effective ways for humans to respond.