Comment by lo_zamoyski

Oh, but they did reach those lands under Marcus Aurelius and indeed occupied them. Prior to his death, he intended to create two new provinces, Marcomannia and Sarmatia. There was even a Roman expedition that reached the Baltic in modern day Poland. (In the case of Poland, it would’ve been a terrible idea to try to conquer those lands, not least of all because they are situated on the indefensible Northern European Plain.)