During the war he rose to the rank of full colonel, with distinguished service in the Battle of Missionary Ridge in Tennessee and the campaigns for Atlanta and Nashville.
In December 1870, he voluntarily left the American army in order to serve with the French military during the Franco-Prussian War.
He was assigned to various military posts in California, Arizona Territory, and the Dakotas, as well as in New York, Virginia, and Washington, D.C.
[3] Augustus and Mary also had a daughter Ethyl and another son, Alger(n)on (sic,[1] who taught Oral Literature Columbia University from 1905 to 1941.
[4] Tassin wrote descriptive and sometimes literary or whimsical accounts based on his army experiences in the American West.