Aquitania had formerly been at the heart of the Visigothic kingdom, but the vast province was lost to the Franks in 507 after the disastrous Battle of Vouille. Ever since then the Goths had dreamed of retaking it, and in 639 they finally saw their chance.
In that year the Frankish kingdom had been engaged in wars on several fronts at the same time - against the Lombards in Italy, the Frisians in Germania, and the rebelling Alemanni at the headwaters of the Rhine. Aquitania was left almost undefended, and King Chintila took the opportunity to cross the Pyrenees and invade. However, after defeating the local levies, Chintila sickened and died, and his son Tulga had to return to Hispania to assert his claim to the throne.
By early 640 the Frisians and Lombards had been defeated. King Dagobert of the Franks, together with his ally Emperor Isaac of the West Romans, put together an expedition to reconquer Aquitania and punish the Goths. In March and April they defeated the Gothic garrisons of Augustoritum, Tolosa, Burdigala and Narbo Martius, then proceeded to invade Hispania itself.
Tulga had still not succesfully asserted his kingship, being challenged by the aged general Chindasuinth. Nevertheless he marched to meet the Franks and Romans, and was promptly defeated and killed a few miles from Caesaraugusta. The allies continued south, sacked Toletum in July, then began a slow return to Gaul, looting and pillaging as they went.
However, with his main rival dead, the Gothic nobles flocked to Chindasuinth's power base in Hispalis to swear allegiance. Chindasuinth immediately marched his army north to try and intercept the Franks, finally catching up with them just north of the Pyrenees. The two armies faced each other at Perpiniarum, but the Franco-Romans withdrew before battle could be joined after receiving alarming news.
The Alemanni had defeated the forces Dagobert had left behind to contain their rebellion, and now the Burgundians had revolted as well. By September the two had formed an alliance with each other and the Goths, and were headed south to confront the Franks. Dagobert and Isaac withdrew in an attempt to escape the closing trap, but only made it as far as Castras, east of Tolosa, before being caught on two sides.
The BattleThe Franks and Romans were camped on the eastern bank of the River Agotis, waiting to cross a nearby ford, while the Goths were camped a mile east and holding them against the river. The Franks felt confident that they could cross quickly and then leave a small force to hold the river against the Goths.
However, on the evening of the 28th September, the Burgundians and Alemanni arrived on the west bank, trapping the Franks. With neither side willing to launch an attack, the armies dug in and fortified their positions. However, while the Goths, Alemanni and Burgundians were able to raid the surrounding countryside for provisions, the Franks and Romans began to starve. By the 7th October their situation was desperate.
On the morning of the 8th the Romans launched a last-ditch attempt to break through the Gothic line and escape to freedom. The Franks soon joined them and the Goths, heavily outnumbered, were slowly pushed back and outflanked.
However, by midday the Burgundians and Alemanni had overcome the river defences, suffering heavy casualties, and joined the battle by attacking the Franks and Romans in the rear. The latter began to rout, pushed through and around the Visigothic line, and fled the battlefield in ruins.
The Franks lost over half the royal army, including King Dagobert himself, while the battered Roman army retreated to Italy where it undertook no further campaigns during Emperor Isaac's lifetime. With Dagobert's death the Frankish realm disintegrated - the Burgundians, Alemanni, Thuringians, Bretons and Frisians all secured their independence, the Goths established themselves in Aquitania, and the remainder was divided among Dagobert's sons who fought constantly among themselves for the next forty years. Dagobert was the last Merovingian king to hold any true authority over all the Franks.
Chindasuinth was confirmed as king of the Visigoths and reigned well for ten years. He was succeeded by his son Reccesuinth in 653, who was succeeded by Wamba, the greatest of all the Visigothic kings.
The catastrophic weakening of the West Romans encouraged Emperor Heraclius of the East Romans to invade and reconquer Italy. However he died at the end of 641 and the expedition was recalled without fighting a single battle. Nevertheless Emperor Isaac did nothing to strengthen his realm, and in 652 he was overthrown in a rebellion led by Gregorius, the Exarch of Africa.
Over the next few decades the Goths grew in power, setting up puppet states in Neustria and Burgundy, until all of Gaul and Hispania recognised their overlordship. They even allied with the southern British kingdoms, offering military support that allowed the Britons to reconquer much of the island from the English. In 674 King Wamba was acclaimed Emperor by the West Romans, bringing the Visigoths to the height of their power.