The Marsi (German: Marser) were a small Germanic tribe settled between the Rhine, Ruhr and Lippe rivers in northwest Germany. It has been suggested that they were a part of the Sugambri who managed to stay east of the Rhine after most Sugambri had been moved from this area.Strabo describes the Marsi as an example of a Germanic tribe who were originally from the Rhine area, now the war-torn Roman frontier, but had migrated deep into Germania.
Tacitus mentions them repeatedly, in particular in the context of the wars of Germanicus. They had been part of the tribal coalition of the Cheruscian war leader Arminius that in 9 AD annihilated three Roman legions under Varus in the Battle of Teutoburg Forest. Germanicus, seeking revenge for this defeat, invaded the lands of the Marsi in 14 AD with 12,000 legionnaires, 26 cohorts of auxiliaries and eight cavalry squadrons. Celebrating the feast of their goddess Tanfana, the Marsi were too drunk to respond effectively to the Roman surprise attack and were massacred. According to Tacitus (Annals 1, 51), an area of 50 Roman miles was laid to waste with fire and sword: "No sex, no age found pity." A Legion eagle from the defeated forces of Varus, either from the XVII or XVIII, was recovered
Enraged by this and other similar bloodbaths (e.g., in the spring of 15 among the Chatti), the frequently quarrelling tribes united once again to fend back the Roman invaders. After two more years of warfare, Rome finally abandoned its efforts to push its boundaries eastward to the Weser river and retreated permanently behind the Rhine.