
Breedlove, 57, succeeded U.S. Admiral James Stavridis as 17th NATO's Supreme Allied Commander Europe (SACEUR) during a handover ceremony in Mons, Belgium.
At a press conference following the ceremony, Breedlove said that his first priority would be to maintain cohesion within NATO as the military alliance is wrapping up its combat mission in Afghanistan.
"NATO forces have become so much more interoperable, so much more capable together because we have been in the conflict together for almost twelve years. What we cannot afford to do is to relax as our posture changes in Afghanistan and to lose that great cohesion," he said.
The general said his second priority was to make sure the alliance was handing over security to a capable force that "can keep Afghanistan secure and prepare for a great future."
NATO Secretary General Anders Fogh Rasmussen, who presided the handover ceremony, said the alliance's focus would remain on Afghanistan.
"On your (Breedlove) watch, Afghan forces will be taking full responsibility for the security of their own country...You will help shape a new and different NATO-led mission: to train, assist and advise the Afghan forces after 2014," he said.
The SACEUR is responsible for the overall direction and conduct of military operations for NATO. The position is normally held by a United States General, who also serves as the Commander of the U.S. European Command.