In spring 1337, many European knights, including Henry XIV, Duke of Bavaria, and nobles from Burgundy and Piedmont, arrived to Prussia for the crusade that was described by Wigand of Marburg.
[1] One of them stayed behind so he could secretly open the gates while the other reported to Gediminas that the fortress was built of logs and poorly reinforced with clay and should be an easy target.
[1] Gediminas brought a large army and siege engines, including battering rams, and besieged Bayernburg on the Trinity Sunday (15 June 1337).
[2] After successfully withstanding the siege, Bayernburg was awarded weapons, food, flag and coat of arms by Duke Henry XIV.
Since the pope decided diocesan affairs, the emperor reissued his privilege on 12 December emitting any references to the diocese.
[2] Repeating this information German historian Caspar Schütz made an error by claiming that the fortress, known as Beyery, was controlled by Kęstutis.
[4] In 1381, Lithuanians commanded by Kaributas, brother of Grand Duke Jogaila, attacked Bayernburg when they learned that it was defended only by a handful of soldiers.
The fortress was captured and burned down in July 1384 by Vytautas when he reconciled with his cousin Jogaila at the conclusion of the Lithuanian Civil War (1381–84).
[2] Due to the supposed death of Gediminas during the attack on the first Bayernburg, debates over its location have received greater attention from historians.
This opinion was accepted by Zenonas Ivinskis and supported by Adolfas Tautavičius who conducted archaeological excavations in Pilaitės in 1965 and found many crusader artifacts.
Edvardas Gudavičius and Alvydas Nikžentaitis identified it with Marienburg, built on the Romainiai island between Veliuona and Pieštvė and destroyed in 1336.
[2] Gintautas Zabiela strongly refuted the idea that Bayernburg stood in Pilaitės as it is too small for a large fortress that could house 200 soldiers and withstand 22 days of attack.