The Flavian Campaign in Hispania, also known as Flavius II's Campaign aginst the Alan Kingdom, was a military campaign organized by the Western Roman Emperor Flavius II against the Alan Kingdom in order to reconquer it. The conquest ended up as a failure however, along with the Romans giving lands to their Frankish mercenaries. This failure led the Senate to lose all trust in Flavius II and to the election of Eucherius as his co-emperor.
In 409, along the Alans, along with other tribes, settled in Hispania, taking various Roman territories. The Alans rapidly becamed the strongest power in the region along with the Romans.
In 422, the magister militum of Hispania, Cassius Cornelius Venantius, helped the Alan Kingdom in the First Hispanian War without the autorisation of the Emperors. He would declare himself Emperor the following year. Although the Alan Kingdom did not participate in the conflict, they did supply it.
In 424, the Western Roman Emperor Flavius I died, leaving Flavius II as the sole ruler. However, he lacked the support of the Senate and always in the shadow of his former co-emperor. In order to leave his own mark, he organized a campaign against the Alan Kingdom. He also convinced many Franks to join him as mercenaries in exchanges of receiving part of the conquered lands.
First Months and Roman Victories
The Alan Kingdom had mainly left its border with Rome unguarded, as the Alan King Attaces believed that should a threat rise, it would come from the Suebi or the Vandals, who he fought in 422. Hoping to take the Alans by surprise, Flavius began his attack before his Frankish reinforcements could join him. He began to wage war and gain victories against the disorganized Alans.
Attaces decided to abandon many cities in order to assemble his troops. He sent many of them to Saguntum, a old Roman city under Alan control near the coasts. Flavius besieged the city, hoping to conquer it before the end of the month. The fights were though for both side, but the arrival of Engilbert and his men allowed Flavius II to conquer the city. The victory was followed by a long celebration.
South of Saguntum was Valentia, the capital of the Alan Kingdom. Attaces had almost as many troops as possible to protect the city. Against all his officers' adives, Flavius decide that he should conquer the city before Christmas. However, Attaces had put traps for the Romans on their way, and by the time of the battle, many of them were tired or hurt from the trip. The battle was hard fought, but ended up with a clear victory for the Alans. Flavius II and his men were forced to return to Saguntum.
Winter and Defeat
During the following months, the Romans mainly kept their forces in Saguntum, while Engilbert and his Franks were tasked to protect the borders of the conquered regions. Flavius refused to go on new attacks against the Alans, believing that their king would soon ask for peace. This "ceasefire" between the two sides left Attaces enough time so that his men from Saltigis and Dianum could join him to Valentia. From there, he launched a surprise attack on the Romans in January, taking them by surprise while they were celebrating. The battle was one sided and forced the Romans out of the city, and soon out of the conquered territories.
After a few small skirmishes, both Franks and Romans were forced to quit the conquered territories. Flavius II and his men went to the city of Ilerda and prepared themselves for a siege. The Alans finally arrived in early March and besieged the city. After a week of battle, the Romans surrendered and Flavius was forced to sign a peace treaty.
The treaty, signed on the 26 March 426, said that the Rome had to give a enormous among of gold to the Alans and that the Alans were free of Roman taxation for trade. Additionally, King Attaces was given the title of governor of Cartaginensis and Lusitania, thus making his rule over his lands legitimate, as it was "given" by Rome and that he was officially governing them for the Emperor. Attaces was the first barbarian ruler to legitimize his kingdom with a Roman title.
In exchange of those concessions, the lands conquered by Attaces were given back to the Romans, as he didn't have enough troops to keep them anyway. Following this, the Western Roman Empire never took any military actions against the Alan Kingdom for the following 25 years.