When Elizabeth Thompson married Maj. Sir William Butler in 1877, she was already a respected painter of military subjects. But becoming Lady Butler gave her a unique opportunity: She could now watch maneuvers in person and even stand in front of charging cavalry to study the momentum of the horses.

The startling result, Scotland for Ever, depicts a head-on charge of the Royal Scots Greys, the cavalry regiment that Napoleon had hailed as “those terrible men on grey horses” at Waterloo.

The painting was an enormous success and became a symbol of British military heroism. The scene is a bit exaggerated — in their famous charge the advancing horses had never reached a full gallop due to the broken ground. But then most of the painting’s admirers would never have guessed that the artist had never witnessed a battle.