Transcript for This day in history: Feb. 15, 2003

Millions of people from New York to London to Rome and in scores of other cities. Took to the streets to protest against any US led invasion of Iraq. It was an enormous display of anti war. And in some cases anti American sentiment. We start tonight with Hilary brown in London where one of the largest rallies took place. Police said that three quarters of a million people march through the streets of London to protest against the war they fear is now inevitable. The rule would create cool and anger on the campus face. Between the Muslims alone and the west. Some had never marched before. Definite in my office demonstration is then you have information to go and anything else. There were huge anti war demonstrations across continental Europe to. Half a million people rally in Berlin. In Rome a million people took to the city's ancient streets shouting no war for oil. In Britain the prime minister Tony Blair is running against mainstream opinion in his Iraq policy. Only hours before this demonstration. Blair was defending it again in a speech to his own Labour Party itself divided on the issue. If we show weakness now. Then it will not the only piece is that it is repeating history. Polls here show that only 10% would support a war in which Britain and the US go it alone. This is a huge political gamble for Tony Blair who is prides himself on being in touch with public opinion. This anti war demonstration here and Hyde Park is being described as one of the biggest demonstrations in British history. It hasn't right across political and socialize. The question is whether this will be enough to change my business. And I was prime minister song. Harry Brown CBC news London.

This transcript has been automatically generated and may not be 100% accurate.