Prime Minister Tony Blair said Thursday night that British forces have joined the U.S.-led war in Iraq "from air, land and sea."
In a televised address recorded hours earlier, Blair said he gave the order for British forces to move on Iraq.
"Tonight, British servicemen and women are engaged from air, land and sea. Their mission: to remove Saddam Hussein from power, and disarm Iraq of its weapons of mass destruction," he said.
As Blair spoke, some of the more than 40,000 British military personnel deployed in the Persian Gulf reportedly joined U.S. forces in a ground offensive in Iraq, crossing over the border from Kuwait.
At home, thousands of Britons joined anti-war protests, including many outside Parliament in London.
"I know this course of action has produced deep divisions of opinion in our country. But I know also the British people will now be united in sending our armed forces our thoughts and prayers," Blair said.
Thanks to Saddam Hussein, the prime minister said, the world faces a new threat "of disorder and chaos born either of brutal states like Iraq, armed with weapons of mass destruction; or of extreme terrorist groups. Both hate our way of life, our freedom, our democracy."