Question: Which mythical character from medieval legend because popular during the era of Romantic nationalism and has a core unit of the Lithuanian Army name inspired by him?

Context articles: Romantic nationalism
Battle of Salis
Lithuanian–Soviet War
National treasure
National mysticism
Lithuanian National Revival
Iron Wolf (character)
Mechanised Infantry Brigade Iron Wolf
Armenian nationalism
Margiris

Romantic nationalism (also national romanticism, organic nationalism, identity nationalism) is the form of nationalism in which the state derives its political legitimacy as an organic consequence of the unity of those it governs.
 This includes, depending on the particular manner of practice, the language, race, culture, religion, and customs of the nation in its primal sense of those who were born within its culture.
 This form of nationalism arose in reaction to dynastic or imperial hegemony, which assessed the legitimacy of the state from the top down, emanating from a monarch or other authority, which justified its existence.
 Such downward-radiating power might ultimately derive from a god or gods
The naval Battle of Salis took place during the Polish-Swedish War (1600-1611) during the night of March 23–24, 1609.
 After the capture of Pärnu, Jan Karol Chodkiewicz, commander of the Lithuanian army, moved towards Riga, which was occupied by the Swedes under the command of Joachim Frederick von Mansfeld.
 Along the way, Chodkiewicz saw a chance to destroy the Swedish squadron based in the Salis port which blocked Riga.
 The dominant presence of the Swedes in the Baltic region gave the Lithuanian army the upper hand, as von Mansfeld and the Swedish army did not expect the possibility of an attack in such a heavily Swedish-occupied region.
The Lithuanian–Soviet War or Lithuanian–Bolshevik War (Lithuanian: "karas su bolševikais" ) was fought between newly independent Lithuania and the Russian Soviet Federated Socialist Republic in the aftermath of World War I.
 It was part of the larger Soviet westward offensive of 1918–1919.
 The offensive followed retreating German troops with intentions to establish Soviet republics in Ukraine, Belarus, Lithuania, Latvia, Estonia, Poland and link up with the German Revolution.
 By the end of December 1918 Soviet forces reached Lithuanian borders.
 Largely unopposed, they took one town after another and by the end of January 1919 controlled about ⅔ of the Lithuanian territory.
 In February the Soviet advance was stopped by Lithuanian and German volunteers, who prevented the Soviets from capturing Kaunas, the temporary capital of Lithuania.
 From April 1919 the Lithuanian war went parallel with the Polish–Soviet War.
 Poland had territorial claims over Lithuania, especially the Vilnius Region, and these tensions spilled over into the Polish–Lithuanian War.
 Historian Norman Davies summarized the situation: "the German army was supporting the Lithuanian nationalists, the Soviets were supporting the Lithuanian communists and the Polish Army was fighting them all."
 In mid-May the Lithuanian army, now commanded by General Silvestras Žukauskas, began an offensive against the Soviets in northeastern Lithuania.
 By mid-June the Lithuanians reached the Latvian border and cornered the Soviets among lakes and hills near Zarasai, where the Soviets held out until the end of August 1919.
 The Soviets and Lithuanians, separated by the Daugava River, maintained their fronts until the Battle of Daugavpils in January 1920.
 As early as September 1919 the Soviets offered to negotiate a peace treaty, but talks began only in May 1920.
 The Soviet–Lithuanian Peace Treaty was signed on July 12, 1920.
 Soviet Russia fully recognized independent Lithuania.
The idea of national treasure, like national epics and national anthems, is part of the language of romantic nationalism, which arose in the late 18th century and 19th centuries.
 Nationalism is an ideology which supports the nation as the fundamental unit of human social life, which includes shared language, values and culture.
 Thus national treasure, part of the ideology of nationalism, is shared culture.
National mysticism (German "Nationalmystik") is a form of nationalism which raises the nation to the status of numen or divinity.
 Its best known instance is Germanic mysticism, which gave rise to occultism under the "Third Reich".
 The idea of the nation as a divine entity was presented by Johann Gottlieb Fichte.
 National mysticism is closely related to Romantic nationalism, but goes beyond the expounding of romantic sentiment, to a mystical veneration of the nation as a transcendent truth.
 It often intersects with ethnic nationalism by pseudohistorical assertions about the origins of a given ethnicity.
Lithuanian National Revival, alternatively Lithuanian National Awakening (Lithuanian: "Lietuvių tautinis atgimimas" ), was a period of the history of Lithuania in the 19th century at the time when a major part of Lithuanian-inhabited areas belonged to the Russian Empire (the Russian partition of the Polish-Lithuanian Commonwealth).
 It was expressed by the rise of self-determination of the Lithuanians that led to formation of the modern Lithuanian nation and culminated in the re-establishment of an independent Lithuanian state.
 Most active participants of national revival were Vincas Kudirka, Jonas Basanavičius and others.
 The period largely corresponded to the rise of romantic nationalism and other national revivals of the 19th century Europe.
The Iron Wolf (Lithuanian: "Geležinis Vilkas" ) is a mythical character from a medieval legend of the founding of Vilnius, the capital city of the old Grand Duchy of Lithuania and modern Republic of Lithuania.
 First found in the Lithuanian Chronicles, the legend shares certain similarities with the Capitoline Wolf and possibly reflected Lithuanian desire to showcase their legendary origins from the Roman Empire (see the Palemonids).
 The legend became popular during the era of Romantic nationalism.
 Today Iron Wolf is one of the symbols of Vilnius and is used by sports teams, Lithuanian military, scouting organizations, and others.
Mechanized Infantry Brigade "Iron Wolf" (MIB "Iron Wolf") (Lithuanian: "mechanizuotoji pėstininkų brigada "Geležinis Vilkas"" ) is the core unit of the Lithuanian Army and forms the country's contribution to NATO collective defence.
 The name of the brigade relates to the Lithuanian mythical character from the medieval foundation legend of the Vilnius city.
Armenian nationalism in the modern period has its roots in the romantic nationalism of Mikayel Chamchian (1738–1823) and generally defined as the creation of a free, independent and united Armenia formulated as the Armenian Cause (Armenian: Հայ Դատ , [hɑj dɑt] or "Hye Dat").
 Armenian national awakening developed in the 1880s in the context of the general rise of nationalism under the Ottoman Empire.
 The Russian Armenia followed with significant causes.
 The Armenian Apostolic Church has been a great defender of Armenian nationalism, with leaders like Khrimian Hayrik who devoted his life to the peasantry.
 The establishment of modern Armenia (1991) and Armenian social fabric becoming more complex gradually decrease the political influence of Hay Dat and shifted towards a modern Armenian nationalism modeled as a liberal nationalism.
 On the other hand, the Armenian diaspora have "diaspora nationalism," which maintain that the threat of assimilation rather than economic advantage.
Margiris or Margis (died 25 February 1336) was a medieval Lithuanian/Samogitian prince, mentioned by Caspar Schütz, via Wigand of Marburg, as the heroic defender of Pilėnai fortress in 1336.
 Not able to defend the fortress against the Teutonic Order, Margiris and other defenders decided to commit a mass suicide, burning the castle and leaving no loot for the enemy.
 This episode from the Lithuanian Crusade was popularized during the 19th-century wave of romantic nationalism and Margiris is treated as a national hero in Lithuania.