This would bind the Archbishopric of Mainz tightly to the Margraviate of Brandenburg and to the imperial party and to which Henry 's father Ulrich V also belonged .
The imperial party was led by Albrecht Achilles .
This would bind the Archbishopric of Mainz tightly to the Margraviate of Brandenburg and to the imperial party , which was led by Albrecht Achilles , and to which Henry 's father Ulrich V also belonged .