When the sixth angel empties his vial of wrath upon the Euphrates River near the end of the last seven years, it will set in motion the events we call Armageddon. The river will dry up allowing the armies of the east to cross over it unhindered. Where will they be heading? Northern Israel is my guess. Honestly, I am not certain that this is the invasion Ezekiel speaks of, but that is my working hypothesis. In that case, the nations that would be involved would include Russia, her Caucasus underlings and her former central Asian republics, Iran, Libya, and Sudan. I don't think it necessary to envision China or India, or even much of the rest of the world as participating. It is possible, but it is not clearly indicated by scripture.
According to Daniel, the Antichrist will find the initial news of these armies stirring alarming. He immediately puts the spin machine into gear and gets out in front of this action. Whatever freelance or rebellious quality these movements may have had at first will be transformed by spiritual deception into a patriotic effort supporting the mission of the Antichrist. Israel, as in the time of Hitler, will be made the fall guy, but I think the key to turning the situation around for the Antichrist may be convincing the world that an alien invasion targeted at Jerusalem is afoot. It's not like mankind isn't being primed for that even now!
Of course, it won't be aliens invading, it'll be Jesus Christ and his church returning! On a rise, somewhere in the Jezreel Valley near Megiddo, the armies flying the banner of the Antichrist will be utterly destroyed. So complete will be their annihilation, it will take the Israelis seven months just to bury the dead. The Antichrist and False Prophet will be caught alive, however, and thrown immediately into the Lake of Fire which burns forever. The Devil will be shackled and thrown into the Abyss, and Jesus and those who have believed in him will begin to rule for a thousand years. Though the Devil has tried to accomplish the Antichrist scheme for so long, when he finally succeeds, he'll falter rather quickly and end up going out with a whimper rather than a bang.
Index to the Entire Series
I, II, III, IV, V