During the early centuries of Roman occupation of Britain the barbarian Irish plagued the coasts with raids. The Romans had made very brief exploratory forays in Ireland and very likely maintained infrequent trading posts there but nothing more. They were instead constantly under threat by these wild men who took great pride in seizing women for Sex slaves and workers. They would come in the worst weather and at night and during times when they were least expected.
It is known that they even sent large military expeditions at times to route the local defenders and damage the Roman reputation there. It was a mark of an Irish war lords reputation that he could mount an expedition over the Irish sea and onto the coasts of the continent and Britain. Very little was known of Ireland but what was known was that it was populated with war hungry fighters who excelled at battle and were lust driven and filled with a desire for taking women. These women would serve as fuck buddies for the warriors and were often married later which then assisted with their integrating with the Irish tribes. The Romans saw them as a threat much as a lion would see the threat in a pack of jackals or hyena’s.
The lion might be able to hold his own against one or two but he could ill afford to turn his back to them and take them lightly. The moment a weakness was found it would be exploited and the Irish were very like this. They were not always a match for the legions in a straight up fight but they would again, seldom fight a straight up fight but instead follow the legions and catch them unawares and fall upon them. They were also fond of setting ambushes and playing a game of deceptive warfare which only the more enlightened Roman commanders could stand against.