H. C. Robbins Landon, has written that the Lord Nelson Mass "is arguably Haydn's greatest single composition. Though in 1798, when he wrote this Mass, Haydn's reputation was at its peak, his world was in turmoil. Napoleon had won four major battles with Austria in less than a year.
The summer of 1798 was therefore a terrifying time for Austria, and when Haydn finished this Mass, his own title, in the catalogue of his works, was "Missa in Angustiis" or "Mass in Time of Distress." What Haydn didn't know when he wrote the Mass — but what he and his audience heard (perhaps on the very day of the first performance September 15) was that on August 1, Napoleon had been dealt a stunning defeat in the Battle of the Nile by English forces led by Admiral Horatio Nelson. Because of this coincidence, the Mass gradually acquired the nickname "Lord Nelson Mass."