In July 1644 he went to Dorsetshire on military service, and on the 3rd of August received a commission as field-marshal general.
Between 1815 and 1847 he rose to the rank of field marshal lieutenant.
On the 11th of October 1808 Haynau had married Therese von Weber, the daughter of Field Marshal Lieutenant Weber, who was slain at Aspern.
He was made field marshal in 1793,and died at Henley-on-Thames on the 9th of July 1795.
This is a Grecian building (1785), with a richly ornamented ceiling and inlaid altarpavement; it also contains much fine sculpture in the memorials to former dukes, and is the burial-place of Field Marshal Lord Raglan, who was the youngest son of the 5th duke of Beaufort.