While engaged in the Attorney-Generalship he was appointed Secretary of the Navy by President Grant.

He was then thirty-nine years of age, and beyond his legal learning was a man of literary taste and general knowledge of affairs.
Mr.Fish and Mr.Robeson were the only members of General Grant's Cabinet appointed the first year of his administration who served throughout his Presidency.
General Grant would not resign his military commission in season for President Johnson to control the Army changes which would follow.
There was no dispute about his immediate successor.

Not only the rank, but the illustrious services, the high personal character, and the popular estimate of Lieutenant-General Sherman established his right to the promotion.

But discussion arose in army circles and among the people as to the Lieutenant-Generalship.

Those holding the rank of Major-General were five in number,--Henry W.Halleck, whose commission bore date August 19, 1861; George G.Meade, August 18, 1864; Philip H.
Sheridan, November 8, 1864; George H.Thomas, December 15, 1864; and Winfield S.Hancock, July 26, 1866.