The construction of the new fortress, located on the south bank of the Mures, marked the history of the town deeply. A team of military engineers directed by Ferdinand Philipp Harsch has designed the Vauban-Tenaille style fortress. The works lasted over 20 years (1763 - 1783) and were carried out by thousands of serfs.
The fortress has a history of its own. The permanent garrison consisted of the Infantry Regiment 33, participant at all major military actions of the Empire. In the centre of the Fortress there is a Catholic Church and in buildings around it Franciscan monks were hosted. Until 1918, the fort also was one of the largest military prisons of the Empire.
During the revolution in 1848/49 the fortress played a crucial role. Under siege of the Hungarian republican army, the garrison bombed the town every day for nine months. In the summer of 1849 the Hungarian revolutionary army succeeded to occupy the fortress for 46 days, before it was encircled by the Russian and Austrian armies and forced to surrender. The Habsburg troops used it once more as a prison and incarcerated 500 officers of the revolutionary army, the majority of them sentenced to death. Among the executed were the 13 generals of the revolutionary army who were hanged respectively shot on October 6th 1849 in the outer pill boxes. In 1752 the emperor Franz Joseph I visited the fortress himself and lessened the sentences of the imprisoned officers.
In the next decades the Arad fortress was a prison for many war prisoners. Between 1914 and 1918 a camp has been improved in the outer pillboxes hosting civilian and military prisoners from Bosnia- Herzegovina.
In November 1918 the fortress has been occupied by French-Serb troops and in July 1919 the Romanian army took it over.