Government crisis and deposition
There were two main reasons why Ulrich V was deposed by his relatives:
The absence of a male heir threatened the survival of the family. In 1375, his father had confirmed the primogeniture decree, which Ulrich II had issued in 1339. The threat was reduced by family treaty of 1391, which allowed his brother Reinhard II to marry if Ulrich V still had no male heir ten years later, that is, in 1401.
Ulrich V ran into economic difficulties from 1394, and even more so after 1396, even though he had received compensation payments from the city of Frankfurt after the Feud of Kronberg. Apparently, he had overstretched himself in his "foreign policy". He mortgaged the village of Hochstadt to Frankfurt, the district of Joßgrund to the Lords of Thüngen, and in the end, he even mortgaged the two major of the four cities in his territory, Hanau and Babenhausen to his neighbor, political rival and first cousin once removed, Archbishop John II of Mainz, effectively making him co-ruler of the Lordship of Hanau.
From c. 1395, a coalition consisting of Reinhard II and his younger brother, John began acting independently and even against Ulrich V. This led to an open dispute, which was settled by a compromise in 1398. However, the dispute emerged again, and grew to the level of a feud. From 1400, and more so from 1402, Reinhard II and John sought support from Archbishop John II of Mainz, who eventually changed sides and dropped his support of Ulrich V.
In 1404, Ulrich V gradually lost power. On 20 February 1404, Reinhard II and John took up government; on 20 November 1404, Ulrich formally abdicated and ordered his subjects to pay homage to his brothers. His wife had already renounced any claims she might have on Hanau earlier that year, in return for a monetary compensation, without Ulrich V being even mentioned in the contract.
Historians in the 18th and 19th century have suggested that Ulrich V may have suffered from a mental disorder. This disorder would have justified setting aside the primogeniture decree for just one generation. However, there is no contemporary evidence to support this theory.
Reinhard II and John ruled jointly at first. After John died in 1411, Reinhard II ruled alone.