The units include some 8,000 troops going to the Iraq war and 7,000 to Afghanistan, all as replacement units to deploy in the summer of 2009.
They are being alerted now to give them the most time possible to complete the training they'll need for their missions and to allow "a greater measure of predictability for family members and flexibility for" their civilian employers, the department said in a statement.
The units for Iraq will be assigned a security force mission including base defense and route security in Iraq and Kuwait. They are:
-The 32nd Brigade Combat Team from Wisconsin. Part of the unit had also been mobilized in 2005 for duty in Iraq.
-The 41st Brigade Combat Team from Oregon. About a third of the unit has already served in Afghanistan.
-The 155th Brigade Combat Team from Mississippi, which has already served in Iraq.
Those going to Afghanistan are:
-The 48th Infantry Brigade Combat Team from Georgia, which already has served in Iraq. It will concentrate on training Afghan National Security Forces.
-The 53rd Infantry Brigade Combat Team from Florida, which left for its first tour in Afghanistan in mid-2006. It is to assume battle space in Afghanistan, where it will perform a full range of operations, the Pentagon said.
While active-duty soldiers and smaller Guard units and members have returned to Iraq for multiple tours, the Guard now is trying to send entire brigades back together to the battlefront on grounds they work more effectively as teams. Brigades generally have about 3,500 troops. Because people come and go from units, it's not possible to immediately determine how many of the people being sent will be going for repeat tours.
Right now Guard members account for roughly a fifth of the Army in Iraq and Afghanistan - dramatically lower than levels during part of 2005, when the Guard soldiers made up about 50 percent of the force in Iraq.
Under a Pentagon policy announced this year, Guard members will serve on active duty for a year.
The announcement affects about 15,000 soldiers, and is part of the regular rotation of forces, according to the Army Times.