He was instrumental in the completion of the frontier fort at San Juan Island and served as the company's acting commander when Captain George E. Pickett was away on leave.

After serving in Washington Territory at Fort Bellingham and Camp Pickett, San Juan Island, Forsyth was promoted to first lieutenant in 1861 and returned to the East to command Union forces in the Civil War.

During the Maryland Campaign he was assigned as aide-de-camp to Major General Joseph K. F. Mansfield until the latter's untimely death at the Battle of Antietam.

In 1863 Forsyth transferred back to the Western Theater to serve as adjutant to General Philip H. Sheridan at Chickamauga.

On January 13, 1866, President Andrew Johnson promoted Forsyth to Brigadier General of Volunteers to rank from May 19, 1865.

[1] On July 17, 1866, President Johnson nominated Forsyth for appointment as a brevet Brigadier General in the regular army to rank from April 9, 1865.

In 1885 Forsyth was in command of Fort Maginnis, Montana where the army was monitoring the Crow, Cree, and the Gros Ventres (Atsina) Indians.

Colonel Forsyth was promoted to the rank of brigadier general to succeed McCook and was appointed commander of the Department of California.

(All in the Regular Army) There have been several attempts by various parties to rescind the Medals of Honor awarded in connection with the Battle of Wounded Knee.

[6][7][8] Proponents claim that the engagement was in-fact a massacre and not a battle, due to the high number of killed and wounded Lakota women and children and the very one-sided casualty counts.

[12] The Army has also been criticized more generally for the seemingly disproportionate number of Medals of Honor awarded in connection with the battle.