He was also one of the Poe brothers, six siblings who were celebrated football players at Princeton University from 1882 until 1901.

[3] During World War I, Neilson served in the United States Army infantry as a lieutenant.

In 1917, at the age of 41, he reported for officers training, located in Plattsburgh, New York.

In 1918, Neilson took part in the Second Battle of the Marne, during which his commanding officer was killed.

During the battle he was wounded, but still took command of his fellow soldiers and safely entrenched them for 24 hours.