I double-took, and recognized exactly what period of history it depicted.
How about you--from what almost universally forgotten event in history is this painting based upon? Here's a hint: look carefully at the sign being sewn on his jacket.It's a spectacular work in person. Hovenden was a great one--he's also responsible for the powerful and more-famous Last Moments of John Brown.
Update--Here is the insignia being stitched to the man's vest:
Answer: The Revolt of the Vendee, and the subsequent genocide, the first of the modern era, done in the name of a secular ideology. The first of a very, very horrific string.