So let's talk briefly about Polish-Hungarian relations, the possible sources the sympathy and friendship between the two nation.
Our history intertwines since the formation of our statehood. In the beginning it was on the level of foreign politics, the Piast and Árpád dynasties strengthened their relation via marriages. Very notable example is our king Saint Ladislaus (ruled: 1077-1095) whose mother was Polish princess. Due to the inner struggles of the House of Árpád, his father prince Béla with his brothers had to fled the country and found safe refuge in the Piast Court, he even led an army of theirs against Pomerania.
Back then the Hungarian dynastic politics had four chief partners: the HRE (with Bohemia), Poland, Kiev and Byzantium. There were other relations, and webs of marriages, but these were the main ones. With the decline of Byzantium, and the Mongol conquest this reduced to the first two, though important marriages were bargained with powers further to west, which helped the Anjou's onto the throne of Hungary after the House of Árpád died out ont he male line.
The strategical nature of our relation with the Polish Kingdom remained intact. First with Bohemia they created the V3 (Congress of Visegrád) which was an alliance and a commercial agreement between the three rulers. Then Anjou Louis I inherited the Kingdom of Poland, and our states formed a personal union. His daughter, Jadwiga followed on the throne (she was canonized recently, another saint of the Polish-Hungarian relations), and her marriage made possible for the Jagiellonians to acquire the kingship. They become not just important partners for the Hungarian rulers, but gave three kings for us as well, one died tragically on the battlefield of Mohács in the struggle against the Ottomans.