Complex sentence: It is well known in Lithuanian history due to the heroic defense of the castle led by the Duke Margiris, when on February 25,1336, it was besieged by the Order of the Teutonic Knights.
Split into simpler sentences: It is well known in the Lithuanian history due to the heroic defense of the castle. The defence, led by the Duke Margiris, took place on February 25,1336, when the castle was besieged by the army of the Teutonic Knights.