William Judd Fetterman was an officer in the United States Army

United States Army

The United States Army is the main branch of the United States Armed Forces responsible for land-based military operations. It is the largest and oldest established branch of the U.S. military, and is one of seven U.S. uniformed services...

 during the American Civil War

American Civil War

The American Civil War was a civil war fought in the United States of America. In response to the election of Abraham Lincoln as President of the United States, 11 southern slave states declared their secession from the United States and formed the Confederate States of America ; the other 25...

 and the subsequent Red Cloud's War

Red Cloud's War

Red Cloud's War was an armed conflict between the Lakota, Northern Cheyenne, and Arapaho and the United States in the Wyoming Territory and the Montana Territory from 1866 to 1868. The war was fought over control of the Powder River Country in north central present day Wyoming...

 on the Great Plains

Great Plains

The Great Plains are a broad expanse of flat land, much of it covered in prairie, steppe and grassland, which lies west of the Mississippi River and east of the Rocky Mountains in the United States and Canada. This area covers parts of the U.S...

. Fetterman and his immediate command were killed during the Fetterman massacre.
Fetterman was probably born in New London, Connecticut

New London, Connecticut

New London is a seaport city and a port of entry on the northeast coast of the United States.It is located at the mouth of the Thames River in New London County, southeastern Connecticut....

, although this is uncertain. His father was a career Army officer of Pennsylvania German ancestry.
Fetterman enlisted in the Union Army

Union Army

The Union Army was the land force that fought for the Union during the American Civil War. It was also known as the Federal Army, the U.S. Army, the Northern Army and the National Army...

 in May 1861 in Delaware

Delaware

Delaware is a U.S. state located on the Atlantic Coast in the Mid-Atlantic region of the United States. It is bordered to the south and west by Maryland, and to the north by Pennsylvania...

, and was promptly commissioned a first lieutenant.