U.S. Army Brig. Gen. Matthew Van Wagenen, deputy chief of staff for operations of NATO’s Allied Rapid Reaction Corps in the United Kingdom, shares warfighting concepts with multinational troops during a senior leader academics seminar in Bucharest, Romania, Jan. 19, 2021, as MNC-SE prepares for a Defender Europe 21 command post exercise. (Photo by Sgt. 1st Class Elvis Umanzor/ U.S. Army)