AGRI DECUMATES Dekumatenland.
Roman region east of the Rhine, extending from the lowest reaches of the River Lahn southwards across the Main to include the valley of the Neckar and the Black Forest.
When the Romans withdrew to the Rhine and the Danube frontiers after their disastrous defeat at German hands in 9 AD, the Black Forest region formed a wedge between the Roman lands west of the Rhine (in modern Alsace) and those south of the upper Danube. In 74 AD the Romans advanced into the Black Forest and the Neckar valley, removing that wedge. At the same time the province of Rhaetia, to the east, was extended northwards from the Danube.
Later a frontier line with walls and ditches was constructed, south from Aschaffenburg on the Main and west from Kilheim (above Regensburg) on the Danube. The two sections met near Lorch, which stood on the River Rems, a tributary of the Neckar, west of Schwäbisch Gmund and east of Stuttgart.
The region from the Black Forest and the Neckar valley to Coblenz was part of the province of Germania Superior and was known as the Agri Decumates. (In a legionary fortress the 10th cohort was stationed near the principal gate, and this countryside was perhaps seen as a gate into the Empire. The prevailing modern view of the origins of the name however is more prosaic – it means ten cantons).
It was abandoned in the 260s or 270s under pressure from the Alemanni, a confederation of German tribes; in the next century they occupied the region.