Francis II, Holy Roman Emperor
Francis II (; 12 February 1768 – 2 March 1835) was the last Holy Roman Emperor, ruling from 1792 until 6 August 1806, when he dissolved the Holy Roman Empire of the German Nation after the decisive defeat at the hands of the First French Empire led by Napoleon at the Battle of Austerlitz. In 1804, he had founded the Austrian Empire and became Francis I, the first Emperor of Austria, ruling from 1804 to 1835, so later he was named the one and only "Doppelkaiser" (double emperor) in history.
For the two years between 1804 and 1806, Francis used the title and style "by the Grace of God elected Roman Emperor, ever Augustus, hereditary Emperor of Austria" and he was called the "Emperor of both the Holy Roman Empire and Austria". He was also Apostolic King of Hungary and Bohemia as Francis I. He also served as the first president of the German Confederation following its establishment in 1815.
East Roman army
In 395, the death of the last sole Roman emperor, Theodosius I (r. 379-95), led to the final split of the empire into two political entities, the West ("Occidentale") and the East ("Orientale"). The system of dual emperors (called "Augusti" after the founder of the empire, Augustus) had been instituted a century earlier by the great reforming emperor Diocletian (r.284-305). But it had never been envisaged as a political separation, purely as an administrative and military convenience. Decrees issued by either emperor were valid in both halves and the successor of each "Augustus" required the recognition of the other. The empire was reunited under one emperor under Constantine I, after 324, under Constantius II, after 353, under Julian, after 361, and Theodosius himself, after 394.