Kingdom of Lithuania (1918)
The Kingdom of Lithuania was a short-lived constitutional monarchy created towards the end of World War I when Lithuania was under occupation by the German Empire. The Council of Lithuania declared Lithuania's independence on February 16, 1918, but the Council was unable to form a government, police, or other state institutions due to the continued presence of German troops. The Germans presented various proposals to incorporate Lithuania into the German Empire, particularly Prussia. The Lithuanians resisted this idea and hoped to preserve their independence by creating a separate constitutional monarchy. On June 4, 1918, they voted to offer the Lithuanian throne to the German noble Wilhelm, 2nd Duke of Urach. Duke Wilhelm accepted the offer in July 1918 and took the name Mindaugas II. However, he never visited Lithuania. His election stirred up controversy, divided the Council, and did not achieve the desired results. As Germany was losing the war and was engulfed in the German Revolution, Lithuania suspended its decision to invite Duke William on November 2, 1918, thereby ending his short reign.
Flag of Lithuania
The earliest known flags with a Lithuanian identity were recorded in the 15th-century "Banderia Prutenorum", written by Jan Długosz. At the Battle of Grunwald in 1410, two distinct flags were present. The majority of the 40 regiments carried a red banner depicting a mounted knight in pursuit. This flag, known as the "Vytis", would eventually be used as the Lithuanian war flag, and again in 2004 as the state flag. 
The remainder of the regiments carried a red banner displaying the Columns of Gediminas. Those that bore the Vytis, also known as the Pahonia, were armies from the Grand Duchy of Lithuania, while those who bore the Columns of Gediminas were from noble families of Lithuania. Until the end of the 18th century, when it was annexed by the Russian Empire, the Grand Duchy of Lithuania used the Vytis as its flag.