Check out this thread
http://forum.thegamecreators.com/?m=forum_view&t=79102&b=21
Scroll down until you find the Machinima tutorial
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Okay, now the story you have would be great for a kids film or a low budget hollywood movie but the amusement only lasts 2 hours; in a game its more like 10.
Here are my ideas for the story: (Trust me: A* in Media Studies, A in English and winner of the "Production" award in the National Political Journalism Competition

)
A nuke, as other people have said, can't be used 3 times. Nor can it detroy an entire country (my homeland

) so how about 3 nuclear missle (each with codenames like Icarus, Phobos and Callisto). When these missiles are spotted, the Government will immediately call for help.
AE's Recipe for Disaster:
The US and Europe join forces in an attack on Britains enemies (Russia, China and the Middle East). Between all this, the eastern Europeans will be torn between the two sides and erupt in civil war. The Asian Nations will join forces and, while Russia hold the western front, they will try to attack the US from the west coast.
Australia will try to stop them but be nuked.
In order to try and get around the European armies, the Middle Eastern countries will have armies move west into Africa and plan to countinue west until they are south of Spain. However, the south africa troops (how are our allies) try to cut them off and get slaughtered...then invaded. The south american countries see that their homeland Spain is in danger and send off millions of troops to Africe and Europa. This leaves them open to attack from the Asian forces in the west...
World war 3, and you want to start it...
AE