Between 5 and 12 million people in over 600 cities worldwide protested against a US war on Iraq yesterday. From reading the police estimates, I suspect it's pretty close to 9 or 10 million. London, Madrid, Barcelona, and Rome had well over a million each, and a large number of cities had 100,000+.
I made a poster [200k, pdf] to help convey the magnitude of the event. Suitable for home, office, or telephone poll use.
Photos from protests on every continent provide a good sense of the massive scale of the event.
Even if it was 4 million, I can't really see how it wouldn't be front page news everywhere. But the politicization of crowd numbers and the power of willful ignorance can never be underestimated. Police managed to whittle the New York City figure down to 100,000 (Organizers say 800,000, Indymedia says 500,000), and CNN talked about "as many as 500,000" in London when the rest of the media was saying one million or more.
That's why I made the poster.