"The military surge into Iraq that began more than 18 months ago has ended. But 150,000 U.S. troops remain, as many as 15,000 more than before the buildup began.

In recent days, the 3rd Infantry Division's 2nd Brigade, the last of the five additional combat brigades sent in by President Bush last year, left the country.

Its departure marks the end of what the Pentagon calls the "surge." And it starts the 45-day evaluation period that Gen. David Petraeus, the top U.S. commander in Iraq, told Congress he would need to assess the security situation and determine how many more troops he could send home."