The unit was sent to secure two violent provinces near the capital, Kabul.
The new troops are the first wave of a surge of reinforcements expected this year after President Barack Obama put an increased focus on Afghanistan. U.S. commanders are thinking of sending up to 30,000 additional soldiers to bolster the 33,000 already in Afghanistan.
A unit spokesman says militants have attacked several patrols with rifles and rocket-propelled grenades. Several roadside bombs also have exploded next to the unit's mine-resistance patrol vehicles, but caused no casualties.
The spokesman says in every case, the soldiers responded with "overwhelming fire."
