On the 14-th of August after 20 days of traveling I got this amazing FDC from Poland. It was devoted to the 600-th anniversary of the Grünewald Battle. This historic events took place on the 14-th of July 1410 in Germany and was a fight between the Order of crusaders under the leadership of Ulrich von Jungingen and the united troops of several East European peoples: Polish, Lithuanians, Russians and Czech under the leadership of Władysław II Jagiełła.
On the stamp you can see the picture of J. Matejko "Bitwa pod Grunwaldem" (The Grünewald Battle) painted in 1878 and which is located in the Polish National Museum - Warsaw.
Thank you very much, Andrzej!\