In 1861, 25-year-old Samuel Clemens answered the call of Missouri's governor to step up and defend his home state. This was governor Claiborne Fox Jackson, a Confederate sympathizer who was forced out of office in July of that year. Missouri never officially seceded from the Union, and its men joined both the Union and Confederate armies. The young man who would later become Mark Twain joined a Confederate unit. However, his "unit" was made up of men who didn't really know anything about the military.
In all, the famed author’s two-week stint as a soldier in the Civil War largely amounted to him larping as a Confederate.
Twain didn't see much action before he gave up and went to stay with his sister in St. Louis, and then headed off to Nevada. But the experience gave him something to write about later as a comedy of errors. His unit tried to retreat once and realized they didn't even know how to do that. Read about Twain's short but comical military service at Historynet. -via Damn Interesting