ghj.sagepub.com/cgi/reprint/19/1/1.pdf

It's not referred to as the Hildesheim Diocesan Feud, but that might work too.

Diocese of Hildesheim (Hildesheimensis).
The old troubles of the see, war and internal feuds, broke out anew and with greater violence than before, until at length the once flourishing see fell a victim to what is known as the "great diocesan war" (grosse Stiftsfehde).

http://www.newadvent.org/cathen/07353a.htm

Bishopric of Hildesheim
After Magnus' death in 1452, the reforms were discarded and conflict broke out again with greater violence than ever before. During the Great Diocesan War, the prince-bishopric was thoroughly crushed by the Dukes of Brunswick. The COmpact of Quedlinburg in 1523 left only three districts, out of twenty seven, to the prince-bishopric while the rest came under the rule of the Brunswicks. The once considerable power of the diocese was ended.
http://history.wikia.com/wiki/Bishopric_of_Hildesheim
Die Hildesheimer Stiftsfehde bezeichnet einen 1519 ausgebrochenen Konflikt zwischen dem Hochstift Hildesheim und den welfischen Fürstentümern Braunschweig-Wolfenbüttel und Calenberg.
The citizens were frequently quarrelling with the bishops, who also carried on wars with neighbouring princes, especially with the house of Brunswick-Luneburg, under whose protection Hildesheim placed itself several times. The most celebrated of these struggles is the one known as the Hildesheimer Stiftsfehde, which broke out early in the 16th century when John, duke of Saxe-Lauenburg, was bishop. At first the bishop and his allies were successful, but in 1521 the king of Denmark and the duke of Brunswick overran his lands and in 1523 he made peace, surrendering nearly all his possessions.
http://www.1911encyclopedia.org/Hildesheim

Conditions were at their worst during what is known as the Münster Diocesan Feud (1450-57). The arbitrary conduct of Bishop Henry II of Moers (1424-50) had aroused a very bitter feeling in the city.
http://en.wikipedia.org/wiki/Bishopric_of_Münster

The territory of the Princebishopric of Hildesheim, to the larger part occupied by the Dukes of Braunschweig-Wolfenbüttel since the GROSSE STIFTSFEHDE (Great Diocesan Feud) of 1519-1523, was reunited in 1643. By then, however, in the area long administrated from Wolfenbüttel the LUTHERAN FAITH had been introduced, while the core territory around the city of Hildesheim had remained Catholic.
http://www.zum.de/whkmla/region/germany/hildesheim16431723.h...

per extensum

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Note added at 6 days (2008-01-03 14:09:17 GMT) Post-grading
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"Stift" (princebishopric) and "Diözese" (diocese) are different entities.