US General Dan McNeill now heads Nato's International Security Assistance Force[AFP]
Richards said at a handover ceremony in Kabul: "Two-thousand-and-six was a year of Isaf and ANSF (Afghan security forces) success and Taliban failure.
"The Taliban did not achieve a single objective."
Isaf offensive
"We have proved that Nato can and will defeat the Taliban militarily and come the spring, an Isaf offensive, not a Taliban offensive, will set the conditions to defeat the insurgents again when inevitably their cynical leaders will launch young men against us to do their dirty business," Richards said.
The US has effectively doubled its combat troops on the ground by extending the tours of duty for some soldiers by four months, which will also provide a rapid reaction force Richards has long demanded but has never been given.
Analysts say there are still not enough foreign soldiers to bolster the under-equipped and poorly-trained Afghan army of fewer than 40,000, and say attention has been diverted by Iraq.
"From the beginning, the United States did not put sufficient forces in Afghanistan in order to prevent a counter-insurgency from re-emerging," Sean Kay, a security expert and professor of international relations at the Ohio Wesleyan University, told Reuters.
The Taliban has warned 2007 would be "the bloodiest year for foreign troops", saying they have 2,000 suicide bombers ready for a spring offensive when the winter snows melt in a few months.