Władysław II Jagiełło (Jogaila) was crowned King of Poland. Jagiello was the Grand Duke of Lithuania (1377–1434) and became King of Poland (1386–1434), first alongside his wife Jadwiga until 1399, and then sole King of Poland. He ruled in Lithuania from 1377. He was born a pagan but converted to Catholicism in 1386 and was baptized as Władysław in Kraków. When he married the young Queen Jadwiga, he was crowned King of Poland as Władysław II Jagiełło. A year later, he converted Lithuania to Christianity. Upon the death of Queen Jadwiga, his reign lasted a further thirty-five years and laid the foundation for the centuries-long Polish–Lithuanian union. He was a member of the Jagiellonian dynasty in Poland that bears his name and was previously also known as the Gediminid dynasty in the Grand Duchy of Lithuania. The dynasty ruled both states until 1572, and became one of the most influential dynasties in late medieval and early modern Central and Eastern Europe. During his reign, the Polish-Lithuanian state was the largest state in the Christian world.
Kazimierz Żegleń (Casimir Zeglen) (dob) was a Catholic priest and a Polish engineer who invented the first bulletproof vest. During his research he came upon the work of Dr. George E. Goodfellow who had written about the bullet resistant properties of silk. Zeglen discovered a way to weave the silk that would create the necessary density to capture the bullet. He produced a 4 ply bulletproof vest measuring 1⁄8 in (3.175 mm) thick, that would protect the wearer from lower velocity pistol bullets of that era. He even tested it on himself in Chicago. He put on a vest of the material and an expert revolver shot fired at the vest at eight paces. Not one of the bullets penetrated the vest.. The weight of the fabric was 1⁄2 lb (0.23 kg) per sq ft (0.093 m²).
Polish Legislative election. The Nonpartisan Bloc for Cooperation with the Government, a coalition of the Sanation faction - won the highest number of seats in the Sejm (125 out of 444) and 48 out of 111 in the Senate. Unlike latter elections during the Sanation era, opposition parties were allowed to campaign with only a few hindrances, and also gained a significant number of seats. The 1928 election is generally considered the last free election in Poland until 1989 or 1991. (sources vary)
The Battle of Kolberg began: The Soviet and Polish forces fought against Nazi Germany for control of the city of Kolobrzeg (Kolberg) in the East Pomeranian Offensive. In November 1944 Kolberg, the Germans established Festung Kolberg, their stronghold in the large Baltic seaport in the Province of Pomerania. It was one of the key German positions in the Pomeranian Wall, a vital link between Pomerania and Prussia. The German High Command planned to use the seaport to supply nearby German forces, and hoped that the stronghold would draw off Soviet forces from the main thrust towards Berlin. The Soviet East Pomeranian Offensive, begun on February 24, 1945 managed to cut off and surround the city and its defenders (mostly from the German Army Group Vistula). Over 80% of the city was destroyed in the heavy fighting. The battle was among the most intense city fights in which the Polish army took part. Polish casualties were estimated at 1,200 dead and missing, and 3,000 wounded. German casualties were 8,000 captured (KIA, data unknown). On March 18, on the day the city fell, the Polish People's Army re-enacted Poland's Wedding to the Sea ceremony, which had been celebrated for the first time in 1920 by General Józef Haller (there was also a lesser known ceremony on March 17)
German submarine U-3508 was bombed and sunk at Wilhelmshaven in an Allied air raid. She would be raised and sunk again on March 30.