Arizona Republican Sen. John McCain, whose fierce independent streak earned him a reputation as a principled and at times frustratingly maverick politician, has died after a months-long battle with brain cancer at the age of 81.

McCain led a storied life that included a career as a naval aviator; a five-and-half year stint in an infamous North Vietnamese torture camp known as the Hanoi Hilton; two presidential runs, including one as the party standard-bearer in which he lost to America’s first African American president; and an influential term as chairman of the Senate Armed Services Committee, a position he used to tirelessly champion increased resources for the U.S. military, while chiding presidents of both parties for, in his view, failing to confront dictators and despots who threatened American democratic ideals.