Sen. John McCainJohn Sidney McCainTo woo black voters in Georgia, Dems need to change their course of action Senate panel again looks to force Trump’s hand on cyber warfare strategy Senate panel advances 6B defense policy bill MORE (R-Ariz.) performed the formal ceremony of pinning the new insignia on Brown, according to the Sun Chronicle of Attleboro, Mass.

Brown had previously served as a lieutenant colonel.

"I never thought I would be colonel," Brown said according to the paper.

Brown called McCain, who has been a mentor to him in the Senate, a national hero.

The junior senator from Massachusetts has served in the National Guard for 32 years.

Throughout the day a number of Brown's Republican colleagues in the Senate congratulated his promotion.