@Walter Hinteler,
Already in April 2014, the U.S. 173rd Airborne Brigade (based in Vicenza, Italy) was sent to Estonia, Latvia, Lithuania, and Poland to join national defense forces in conducting exercises and shoring up security in the region.
These units were replaced with units from the 1st Cavalry Division and the 3rd Infantry Division.
The 3rd Squadron, 2nd Cavalry Regiment, also undertook the "Dragoon Ride", a 1,100-mile convoy of over 600 soldiers and 120 military vehicles across six European countries in March 2015.
In 2015, 5,200 German soldiers were in Poland and the Baltic states on exercise. One German bataillon (still) is under Polish command.
Besides that, there's (since 1999) the Multinational Corps Northeast (mainly consisting of German, Polish, and Danish units), headquarters are in Poland.
In June 2016, during the exercise Brillian Capability 2016, the Corps has become operationally capable to assume command of the
Very High Readiness Joint Task Force, also referred to as the "spearhead force".