US Defence Secretary Leon Panetta said Allen has proven himself to be one of the most outstanding battlefield leaders, a brilliant strategist, and an exemplary Marine.
"I will be forever thankful that the international effort in Afghanistan was in General Allen's capable hands during much of my tenure as Secretary of Defense. His leadership over the last 19 months will long be remembered as pivotal to this campaign," he said.
"The strategy he developed and implemented has put us on the right path towards completing this mission, with Afghan forces now on track to step into the lead for security nationwide this spring and to assume full security responsibility by the end of next year," Panetta said.