john mccainSen. John McCain of Arizona shares a laugh with one of his closest friends, Sen. Lindsey Graham of South Carolina.Chip Somodevilla/Getty Images

Republican Sen. John McCain, 81, has died after a long battle with brain cancer.

The Arizona senator was diagnosed with an aggressive form of glioblastoma and began treatment for the disease in July 2017.

McCain appeared to be undeterred for several months after his diagnosis was made public.

He was seen back at work on Capitol Hill last fall and weighed in on major legislative policies, including the annual defense authorization bill and efforts to repeal the Affordable Care Act.

“I don’t mean to be repetitious, but to my Democrat friends and some of my Republican friends: I’m coming back,” McCain said during a Facebook Live event in August last year.

McCain made headlines upon his return — including when he dramatically voted no on the Republican version of a bill to repeal the Affordable Care Act.

His career as a public servant spanned decades of honorable service, and despite some challenges along the way, McCain established himself as a key figurehead of the Republican Party. Few lawmakers on Capitol Hill will match the legacy he leaves behind.

Here’s a look back at John McCain’s incredible life: