In separate releases, the service identified the deploying units as the 1st Stryker Brigade Combat Team, 4th Infantry Division; and the 2nd Infantry Brigade Combat Team, 4th Infantry Division. Both brigades are based at Fort Carson, Colorado.
The Army didn't specify how many troops would be affected by the orders.
"To balance the need for transparency with operational security, the Army will not provide specific numbers on deploying operations capabilities such as forces and equipment," Aleah Castrejon, a spokeswoman for the division, said in a brief telephone interview with Military.com.
A brigade typically numbers between 3,000 and 5,000 soldiers.
The 1st Stryker Brigade Combat Team, 4th Infantry Division, will replace the 4th Brigade Combat Team, 25th Infantry Division, while the 2nd Infantry Brigade, 4th Infantry Division, will replace 1st Infantry Brigade Combat Team, 82nd Airborne Division, according to the Army.
"The 1st Stryker Brigade Combat Team, 4th Infantry Division, is trained and ready for any mission in the Army," Col. Monté L. Rone, the brigade's commander, said in a release. "Our formation of soldiers are fit, inspired, disciplined, and trained. We couldn't do this without our families and owe a special thanks for their willingness to stand by our most precious resource -- The American Soldier."
"The 2nd Infantry Brigade Combat Team of the 4th Infantry Division has a proud deployment history in support of operations in Afghanistan," Col. David Zinn, the unit's commander, said in a release. "Our War Horse soldiers are trained, ready, and are honored that the Army has selected our unit for the deployment."
The deployments are part of a regular rotation of forces to support Operation Freedom's Sentinel, so they're unlikely to significantly alter the total number of U.S. service members in country.
While Pentagon officials have been reluctant to disclose the number of U.S. troops on the ground in combat zones, the Defense Manpower Data Center's most recent quarterly report listed 8,992 American service members in Iraq, 1,720 in Syria and 15,298 in Afghanistan.
The U.S. military has ramped up airstrikes in Afghanistan this year.
The Air Force's monthly bombing campaign in the country hit a five-year high in August. That came a few months after it dropped its biggest non-nuclear bomb on the ISIS Khorasan terrorist branch and a few months before unleashing the F-22 Raptor stealth fighter to bomb Taliban drug labs.
Even so, the Taliban still control or influence 54 of 407 districts in the country, or 13 percent, according to an October report from the Special Inspector General for Afghanistan Reconstruction, or SIGAR.