Annex D: Battle of Idistaviso
The Roman writer Tacitus provides in the Annals II the following information about the Battle of Idistaviso:
Germanicus planned in the summer of 16 CE for the attack on the Cherusci to transport the legions by ship, and thus to be able to use the surprise effect. The gathering point of the army was the fork of the Rhine and Waal. The meeting point of the legions transported by ship and the cavalry was the Ems mouth. During the march in the direction of the Cherusci, the Angrivarian auxiliary troops seperated from the Roman army. At a Weser ford the Romans met the Germanic army, which camped on the eastern side of the Weser. The next day, the Germani had set up for battle on the eastern bank of the Weser. The Roman cavalry and Batavian auxiliary troops crossed the Weser, and there was a first combat. The Cherusci pretended to flee and lured the Batavian auxiliaries into a plain surrounded by wooded heights, where the Batavi were surrounded and suffered heavy casualties. After the first combat, the entire Roman army crossed the Weser and moved to a place closer to the Elbe than to the Rhine. In the following, the Germani turned to fight in the plain of Idistaviso. The plain of Idistaviso lay between the Weser loops and a range of hills, in the plain there was a forest area. Part of the Germanic army was positioned in the open plain and in the forest area, the Cherusci had occupied the range of hills to attack the Romans from an elevated position. The Roman army moved into the plain, and then attacked from the marching order. The Cherusci storming down from the hills were attacked by the Roman cavalry in the flank and in the back. The rest of the Germanic army moved seemingly haphazardly between the open field and the forest area. The battlefield was 10 000 steps (about 15 km) long.
Tacitus further describes an effortless as well as overwhelming victory. A short time later in the Battle of the Angrivarian Wall the Germanic army nearly defeated the Romans, thus a heavy defeat of the Germani at Idistaviso and the associated weakening of the Germanic army seems unlikely. More likely appears a feigned battle with a fake defeat of the Germani, which should animate the Romans to pursue the seemingly defeated German army in order to lure the Romans there, the very Angrivarian Wall.
The course of the battle
The starting point of the battle at Idistaviso, which as the further remarks show can only be seen in connection with the Battle of Angrivarian Wall, is the mouth of the Ems river in the area of today's Leer. Possibly also the archeologigal site Bentumersiel is related to Germanicus' campaign of the year 16. From here Germanicus' army moved in the direction of the Cherusci, whose settlement areas layed between the Weser river and the Harz. The western settlement area of the Cherusci and thus fastest to reach for the Romans was the Weser Uplands. The shortest connection between the Ems mouth and the Weser Uplands leads via Minden, which is why the Romans used the Weser ford near Minden to cross the Weser towards the east. On the way from the Weser mouth to Minden the Angrivarian auxiliary troops withdraw from the army, as the further remarks show in the direction of Kalkriese, where with the construction of the Angrivarian Wall an ambush was prepared for the Romans.
Fig. D-1: Battle of Idistaviso, the Roman army marches to the Weser (blue), the Angrivarian auxiliary troops withdraw from the army (orange)
The Romans reached the Weser ford near Minden, and there was a first combat between the Romans and the Germani, which had set up for battle the next day on the eastern bank of the Weser. Germanicus sent the Roman cavalry and Batavian auxiliary troops under their leader Chariovalda across the Weser in order to attack. The Cherusci then pretended to flee, and in this way lured the pursuing Batavi into a plain surrounded by wooded heights. The only plain that lays in marching distance and that is surrounded by hills is located near Bad Eilsen, between the hills Harrl and Bückeberge in the north and the Weser hills in the south. Thus in the plain near Bad Eilsen the Batavi were surrounded by the Cherusci and suffered heavy casualties, until the Roman cavalry came to their aid.
Fig. D-2: Battle of Idistaviso first combat, Roman army (blue rectangle), Germanic battle formation (red triangles), attack of the Roman cavalry (blue), attack of the Batavi (turquoise), pretended retreat of the Cherusci and encirclement of the Batavi (red)
After the first combat, the entire Roman army crossed the Weser. In the following, Germanicus said in a speech to the army that they had reached a place that was closer to the Elbe than to the Rhine. From this it can be deduced that the Romans moved from the Weser initially further east in the direction of the Elbe, thus approximately in the direction of the Hildesheim Börde, an agricultural profitable area, where possibly additional provisions could be requisitioned. From this far eastern place Germanicus led the army into the plain of Idistaviso, where the Germani had once again set up up for battle. According to Tacitus, the plain of Idistaviso lay between Weser loops and a ridge of hills, and in the plain there was a forest area. The only place to which this description applies is the Weser valles between Hessisch Oldendorf and Rinteln, which the Romans reached from the east via today's Hameln. Tacitus also mentions a forest area, which was in the back of the army column. Since the valley was used with high probability for agriculture or pasture management, the forest area was in the area of the hills of today's nature reserve Heineberg. This means the majority of the Germanic army took position in the valley between Rinteln and the Heineberg, the Cherusci positioned themselves along the ridge of the Weser hills to attack from this elevated position.
Fig. D-3: Battle of Idistaviso starting position, Roman army (blue), positions of the Cherusci (orange), remaining Germanic positions (red)
The battle of Idistaviso began, the Romans attacked from the marching column, and immediately the Romans seemed to have the control. The hostilities of the Germani were apparently disoriented, the Germani changed their positions without any apparent purpose, and many withdraw across the Weser. Tacitus reports on many killed Germani, however as mentioned above a short time later at the Angrivarian Wall the Romans faced again a strong Germanic army, therefore the losses of the Germani must be kept within limits. The scenario described by Tacitus and the limited losses of the Germani therefore suggest a distraction maneuver. In this distraction maneuver Arminius and the Cherusci had taken over the hardest part, as they had to break through the Roman marching column, in order to also be able to withdraw across the Weser. In addition, the Cherusci were encircled by the Roman cavalry. Accordingly, Tacitus reports that Arminius was engaged in fierce fighting, but perhaps Chauci auxiliaries in the Roman army had helped the Cherusci to break through the Roman lines.
Fig. D-4: Battle of Idistaviso, attack of the Romans from the marching order (blue), fictitious attacks of the Germani and retreat over the Weser (red), encirclement of the Cherusci by the Roman cavalry (turquoise), breakthrough of the Cherusci through the Roman marching column and retreat across the Weser (orange)
For the time after the Battle of Idistaviso Tacitus reports on further Germanic disturbance attack on the Roman army column, and that the Germani chose the next battlefield. The Germani thus conducted the local course of the further combat operations, and lured the Roman army along the Hellweg unter dem Berg to a well-prepared trap: the Angrivarian Wall (s. Annex E).
Fig. D-5: Germanic disturbances (red) after the battle of Idistaviso direct the Roman army (blue) to the Angrivarian Wall at Kalkriese (red mark)