Players assume the role of President Bush in the online game, receiving regular briefings from caricatures of Defence Secretary Donald Rumsfeld, Secretary of State Colin Powell and national security adviser Condoleezza Rice.
It starts with Baghdad's quick fall but then proceeds to an Iraqi anthrax attack on Israel, a retaliatory nuclear strike, revolt in Saudi Arabia, and a Kurdish coup in northern Iraq.
Once Saddam Hussein's body is found, players are asked to select one of three look-alike successors, who soon requires military backing to fend off an anxious Iran.
There are also anti-American uprisings in Egypt, Jordan, Lebanon, Syria and Pakistan, which lead eventually to nuclear warheads being smuggled to militant groups.
"This is a projection of the most likely outcome of a new war in the Gulf," reads the website idleworm.com, home of the game created in November by 33-year-old Dermot O'Connor.
O'Connor, a computer animator who moved from Ireland to California three years ago, drew his source material from interviews and reports in the Atlantic Monthly, The Washington Post, The New York Times, the Times of London, the Guardian newspaper in Britain and the Australian Sunday Herald.
The game appears interactive but leads players down a set path, designed by O'Connor to highlight the risks of war.
"There is only one deliberate outcome. It didn't make sense to give people the idea that they could avoid the worst," he said in an interview.
About 20 000 people play the game every day, he said.
O'Connor said "a constant pressure and drum beat" for war was clouding American perspectives on what could happen after an initial conflict and he felt the "worst case scenario" charted in his game offered an accurate reflection of the potential perils of attacking Iraq.
"I don't see how (the Bush administration) can do it without creating a mess," he said. "I just don't see that the war is worth the risks."