Britain's connection with Rome began, not in AD43, but in 55BC, when Julius Caesar first attempted to invade from the German coastline, where he had previously been engaged attempting to subdue local tribes. The invasion of Britain may have been the result of two possibilities, as his modern biographer Christian Meier suggests. The first of these is that the Gauls (French) had been employing British mercenaries against him, the second that he suspected Britain to be a land of 'great riches' . The landings, however, proved to be less glorious than intended. Fierce resistance was encountered from the Cantiaci, Catuvellauni and Trinovantes tribes, and due to a lack of cavalry, Caesar found that he could not pursue the retreating Britons as he would have liked. Perhaps surprised by the strength of the resistance, Caesar returned to the continent for the winter, and began preparing for another attempt in the following year. His commitment to the subjugation of Britain is demonstrated here, when he ordered the construction of a great number of ships, and had the existing fleet repaired and modified to make disembarking easier. The fleet involved in the invasion of 54BC consisted of more than 800 vessels and it was to transport an army of five legions and some four regiments of cavalry. The second campaign saw a forceful drive through the tribal territories and across the Thames, made easier by the fact that the assembled British army were frightened by the sight of so many ships, and had quitted the shore to conceal themselves on higher ground. Despite offering determined resistance inland, the British had to surrender, and Caesar demanded that hostages be given. More importantly, he forced the tribes to begin paying tribute to Rome, and it is this act which bears more political significance than any other. From this point on, trade links with the continent, which may have existed before, were definitely in use. The British tribes that had offered resistance could now experience some of the luxuries of Roman rule. These links with Rome were to prove invaluable to the Emperor Claudius' campaign almost exactly a century later.

In a world where military triumph was of the utmost importance, Claudius needed to secure his position as Emperor and Britain seemed the perfect country to conquer. However, despite the energy Caesar committed to subduing the land, the enthusiasm seems to have waned through time. Even long after Britain was a Roman province, Claudius' biographer Seutonius, (who wrote during the reign of Hadrian (AD117-38)), commented that 'Claudius's sole campaign was of no great importance'.

The invasion was made easier by the fact that the British tribes had been falsely informed by the Gauls that the Romans had revolted and the invasion would not take place, causing them to abandon the defensive positions they had taken. Claudius' force consisted of four legions (II Augusta, IX Hispana, XIV Gemina and XX Valeria) and supporting auxiliaries, totaling around 40,000 troops. After the initial landings at Richborough, the invading army marched to the river Medway, where it saw its first victory against an assemblage of British tribes. They legions then marched to the Thames, where they halted to allow Claudius to join them and lead them to victory. With the Emperor at their head, they marched further on to Camulodunum (Colchester), the British capital. When this was taken, Claudius formally recieved the submission of the south eastern tribes and declared Camulodunum the capital of Roman Britain. From Camulodunum, the legions marched out to conquer the rest of the island. Legio XX was held in reserve in Camulodunum, Legio II ventured to the southwest, Legio XIV went to the midlands and Legio IX went north. It is at this point that Lincolnshire first encountered the Roman Imperial army.

The tribe occupying Lincolnshire at that time were the Corieltauvi, although theit territory also included Rutland, Nottinghamshire, Leicestershire and northern Northamptonshire. Although living considerably further north than the more romanized tribes of the south east, the Corieltauvi minted their own coins, and had their own potters producing work of a similar quality to the southern tribes. The settlements of the tribe were similar to that of any other British tribe - circular huts contained within a banked and ditched enclosure. One area in which Lincolnshire differs from other regions of the country is the lack of hillforts, large defensive structures, constructed for inter-tribal warfare rather than as anti-Roman fortifications. Although Lincolnshire has none, or at least none yet positively identified (there is an unproven theory that the site of Lincoln Castle was once a hillfort), the Corieltauvi did construct them, as is proved by the Breedon-on-the-Hill site in Leicestershire.

Legions on the march constructed temporary camps to house the Legionaries overnight or longer. Aerial photography has discovered two such camps at Longthorpe, near Peterborough, and Newton on Trent . It is well known that Legio IX were to eventually found the fortress at Lincoln, but these camps were used before this, while the Legion was on campaign. By AD47 a northern border was established, running from Lincoln to Exeter on the line of the Fosse Way, the modern A46. Another famous Roman road, Ermine Street, was also used in the advance northwards. Along the line of the road, forts were established to ensure a military presence was retained as the army moved northwards. Two such forts were established at Ancaster and Great Casterton. With the surrounding countryside controlled, Legio IX began to set up a more permanent headquarters at Lincoln. Although the Romans constructed forts and camps as they advanced, there is no evidence to suggest that the Corieltauvi were a troublesome tribe, and the military presence can be attributed more to the Roman's adherence to guidelines regarding warfare than the need to forcefully conquer the tribe. There is interesting evidence, however, in the form of Corieltauvi coin hoards discovered in Yorkshire, and dating to between AD25 and AD30. Whilst these may be simply attributable to trade, there is also the possibility that members of the tribe may have fled their homes as news of Legio IX's progress reached them.