[cnn-photo-caption image= http://i2.cdn.turner.com/cnn/2008/WORLD/asiapcf/12/13/gates.afghanistan/art.gates.gi.jpg caption="U.S. Defense Secretary Robert Gates speaks to U.S. troops at Joint Base Balad in Iraq on Saturday."]
BAGHDAD, Iraq (CNN) - U.S. Defense Secretary Robert Gates, who arrived in Iraq in a surprise visit Saturday, said he doubts U.S. troop presence in Afghanistan will reach the levels attained in Iraq.
The Soviets, who invaded Afghanistan in the 1970s but left in early 1989 after failing to control the country, had 120,000 troops but lost because they didn't have the support of the people, Gates told troops at Balad Air Base, just north of Baghdad.
The U.S. military has about 31,000 troops in Afghanistan, less than a quarter of its total strength in Iraq.
Gates' predecessor, Donald Rumsfeld, made similar comments in a 2005 Senate hearing about the Soviet presence in Afghanistan. At the time, Rumsfeld was dealing with a conflict of a different nature, but the comments arose while he was defending what critics called insufficient U.S. troop strength in Iraq.