In short the tribulation is first and is a man made event. Nothing remotely supernatural. THe watchtower stated last year (2004) that they had no idea if it had alrady started, but they would know when it was about to be over (no duh), and related it to a woman in labor. Mathmatically the tribulation could last for days, to centuries, and is basically the a new generation of the crusades which erode the human race to near extinction (anyone thinks this sounds weirdly like battle tech).
After in general most (all ) of the "religious" people are dead (I never understand this part) magically out of no place Satan mattereallizes along with his demon army and decides to kill the anointed (using bad jw math less than 8000 people which makes you wonder why he has not did it already). This starts armageddon. Now idiots of the world who apparently don't think Satan is bad, or assumes Jesus is evil Join satan for the sole purpose of killing anointed people that seem to be mostly gereartic, megalomaniacs, or slightly insane. Jesus comes nukes satan and the army of idiots (hmm maybe Jesus was evil) and armageddon is over. All the non idiots that did not try to box with god get to burry the corpses and live in Jesus' new communist police state. Oh maybe thats why people join Satan.
This doctrine seems to be imploding under the "WTF was Franz smoking" clause article nine.