The Grand Duchy of Dacia is based on the Latin name that was given to ancient Romania/Bessarabia. According to Tanya's knowledge, Dacia is a minor state that had yet to achieve industrial revolution.
Their main military power comes from the old way of doing a conscription or peasant levy. These are non professional and untrained soldiers mostly. Their invasion of the Empire started with a march, they failed to establish air superiority with mages and planes as well as bombard positions with artillery. Their vanguard force was thrown into turmoil by Tanya Degurechaff's 203rd Aerial Mage Battalion.
The Dacian War ended shortly as the Imperial Army routed the Dacian force with with the unprecedented odds of 70,000 against 600,000. Dacia is overrun in six weeks. By the time Os city fell, the Empire had already established full control of Dacia and was smoothly setting up their administration.
Little is known about their diplomatic relationships with other country, but Tanya suspected their declaration of war was most likely incited by either the Republic or other nations that would have benefited from the Empire having to fight a three-front war.
Dacia was indeed sponsored by the Francois Republic to join the war and used the Casus bellis of taking back their land from the Empire. Apart from the factory there is no known knowledge of foreign influence within the Grand Duchy of Dacia.
The military of Grand Duchy of Dacia was still stuck in a late-19th century paradigm, thinking in only 2 dimensions which is land forces exclusive. The Grand Duchy of Dacia has failed to develop a proper and trained army, establish a mage unit, construct an air force and a long range bombardment artillery. They held a remarkable amount of troops standing strong at 600'000 but failed to make proper use of them. They employed single shot revolving rifles with stripper clips, no automatic weapons are known. They have no known air capabilities nor any defenses against aerial assaults. The Kingdom of Dacia had old artillery seen for musket lines but nothing capable of long range or flak..
- On the maps that show up in the background of the anime, the country's name shows up as "Grosherzogtum Dacia" in a highly stylized font.
- In the anime, the weapon making scene inside their weapon factory shows workers making artillery shells.