Germany during the Crusades
Lothair of Supplinburg (1125-1137)
Lothair operated under a number of burdens. He was chosen mainly because of what he was not: he was not overly powerful, he was not connected to the Salian house, and he was not likely to be a strong emperor. He spent much of his reign either fighting against Frederick of Swabia, or else trying to assert his authority among those who were supposedly his allies.
Over the course of his reign, a great rivalry coalesced. On the one side were the partisans of Swabia, whose family was known as the Hohenstaufen. On the other side, adhering to not so much to Lothair personally as to the potential gain he represented, was the Duke of Bavaria and his family, the Welfs. These two factions (for they were more than just families) came to dominate German politics for the rest of the century. Their feud spilled over into Italy, where they were known as the Guelfs (Welfs) and the Ghibellines (Hohenstaufen)., and in that form persisted in Italy long after the feud was ended in Germany.
As for Lothair himself, he died childless and so the succession was again open. As Henry V had done before him, Lothair designated an heir, but as with Henry, his will was thwarted. Lothair had chosen his son-in-law, Henry the Proud of Bavaria. In fact, he had also made Henry the duke of Saxony, so that Henry would have been Duke of Bavaria, Duke of Saxony, as well as King of the Romans.
This was going too far for the other German princes. They blocked the Welf Henry's succession, choosing instead a candidate from the Hohenstaufen side, Conrad of Swabia.