Now here's an irresistible headline: Marked men: The tattoos of New York Irishmen 1863.
You'll find the curious story revealed, together with the names and tattoo details of a few hundred Irish men, on the Irish in the American Civil War blog, a high quality and informative blog written by conflict archaeologist and historian Damien Shiels. Damien is also author of a 256-page book, published earlier this year, with the same name as his blog.
Both publications tell the often forgotten role of the 200,000 Irish men and women who were involved in various ways in the US Civil War. I recommend both, and not only to those whose Irish ancestors may have some connection to the War.