While serving as the commander of Fort Stevenson in Dakota Territory from 1867 to 1870, he was promoted to the brevet grade of brigadier general in the regular army in 1868.

His father's service to the previous king, Charles X, meant that Trobriand was excluded from serving the new one, Louis Philippe, after the July Revolution of 1830.

In 1841, to answer a dare, Trobriand emigrated to the United States at the age of 25 and immediately became popular as a bon vivant with the social elite of New York City.

Soon after, Trobriand was debilitated with a malady diagnosed as "swamp fever", missed the remainder of the campaign, and was unable to return to duty until July.

They successfully held out until relieved by units of Maj. Gen. John C. Caldwell's division of the II Corps, but it came at a terrible price—every third man in Trobriand's brigade was a casualty.

This officer is one of the oldest in commission as colonel in the volunteer service [and] has been distinguished in nearly every engagement of the Army of the Potomac, and certainly deserves the rank of brigadier-general of volunteers, to which he has been recommended.Despite the recommendation and his excellent performance at Gettysburg, Col. Trobriand did not receive a promotion to brigadier general until his appointment to that grade by President Abraham Lincoln on April 10, 1864, to rank from January 5, 1864, after the U.S. Senate had confirmed the appointment on April 7, 1864.

[3] On December 3, 1867 President Andrew Johnson nominated him for the brevet grade of brigadier general in the regular army, to rank from March 2, 1867 and the U.S. Senate confirmed the award on February 14, 1868.

In November 1866 he received word of having been appointed by General Ulysses S. Grant as colonel to command the 31st Regiment of Infantry, but requested a leave of absence to complete a book about his war experiences and the Army of the Potomac.

[6] While in North Dakota, Trobriand painted a series of landscapes and portraits of friendly American Indians of the region: the Arikara, Gros Ventre, and Mandan peoples.

[1] He next served as commander of Fort Shaw in Montana, where hostilities had been high between settlers and members of the Blackfoot Confederacy, who had historically occupied the territory.

He explicitly ordered protection of friendly bands, but the Army mistakenly[citation needed] attacked one in the Marias Massacre of January 23, 1870, to national outrage.

In September 1874, 5,000 members of the White League had taken over state offices in the city for three days, in an attempt to turn out the Republicans.

[7] During this period of dissolution of the Reconstruction government, despite speeches against interference with the legislature, individual Democrats praised Trobriand for his delicate handling of the situation.

[8] After President Grant withdrew federal troops from New Orleans in January 1877, Trobriand accompanied them to Jackson Barracks, outside the city on the Mississippi River.

He was ordered to Pittsburgh, Pennsylvania in July 1877 to command federal troops there against labor riots in the Great Strike, but these were suppressed by city and state forces[9] after much property damage.