The Wendish Crusade (German: Wendenkreuzzug) was an 1147 campaign, one of the Northern Crusades and also a part of the Second Crusade, led primarily by the Kingdom of Germany inside the Holy Roman Empire and directed against the Polabian Slavs (or "Wends").
By the early 12th century, the German archbishoprics of Bremen and Magdeburg sought the conversion of neighboring pagan West Slavs to Christianity through peaceful means. During the preparation of the Second Crusade to the Holy Land, however, a papal bull was issued which supported a crusade against these Slavs.
The Slavic leader Niklot preemptively invaded Wagria in June, 1147, leading to the march of the crusaders in late summer, 1147. They achieved an ostensible baptism of Slavs at Dobin and were repulsed from Demmin. Another crusading army marched on the already Christian city Szczecin, whereupon the crusaders dispersed upon arrival.
The Christian army, composed primarily of Saxons and Danes, forced tribute from the pagan Slavs and affirmed German control of Wagria and Polabia, but failed to convert the bulk of the population immediately.
When the Second Crusade was called, many south Germans volunteered to crusade in the Holy Land. The north German Saxons were reluctant. They told St Bernard of their desire to campaign against the Slavs at a Reichstag meeting in Frankfurt on 13 March 1147. Approving of the Saxons' plan, Eugenius issued a papal bull known as the Divina dispensatione on 13 April. This bull stated that there was to be no difference between the spiritual rewards of the different crusaders. Those who volunteered to crusade against the Slavs were primarily Danes, Saxons, and Poles, although there were also some Bohemians. The Papal legate, Anselm of Havelberg, was placed in overall command. The campaign itself was led by Saxon families such as the Ascanians, Wettin, and Schauenburgers.