You live in Washington DC have lived there for weeks but something happed 2 years ago in 2003 in New Mexico and now the city is under martial law because of a alien Race known as "xen" but something is happening, a massive portal opens above DC and a massive space ship comes out of it it has begun, a Invasion from a modern alien race known as "The Universal Union" or "The Combine", The massive ship begins to drop landing craft into the City

What do you do?