The Invaders came from outside the Earth. They came at first in cylinders  that slammed into the rural areas around England, Austria, Spain and the United  States. Quickly following the cylinders however were saucers manned by the  Grays. The Overlords soon began assembling their tripod fighting machines and  there was war that spanned the planet. This war was different for the Great  Powers because the war was not for territory or resources but for the very  survival of the human race. 
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And for one very brief shining moment mankind over game it's differences to  unite ageist a common foe. Combined armies of the great powers and minor nations  manned the barricades, erstwhile blood enemies counter attacked all over the  globe. British Indian forces with Pathan support ambushed an enemy force in the  Khyber Pass. Russian and Japanese forces took heavy losses but over came the  enemy on the Kamchatka Peninsula. American, French, and British fleets inflected  a severe defeat on the enemy off the coast of Cuba. Turkish and Persian forces  drove the invaders out of Basra.
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The best minds that mankind could  produce met in secret in a basement of a destroyed building
in Zurich  Switzerland, with prize pieces of captured alien technology. From this meeting  and others around the world new weapons were fashioned to carry the fight to the  enemy. Nor was this humanities only hope for in this crisis many otherwise  unknown and untried inventors came to the fore. One young inventor, mechanical  engineer, and electrical engineer named Nikola Tesla perfected his electrical  death ray that disrupted the Grays saucers as well as the mind link that the  Masters used to coordinate their attacks.
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The tables had at long last  began to turn....