Vigils have taken place in London, Philadelphia and Germany for Chelsea Manning on her fourth birthday behind bars.
Manning is at Fort Leavenworth in Kansas and serving 35 years for leaking classified material to the website WikiLeaks. She was sentenced in August.
Her supporters say she exposed alleged war crimes undertaken by the US Military in Iraq.
Fort Leavenworth is refusing to provide Manning with gender confirmation treatment.
She wrote: “I’m also grateful for having social and human justice pioneers who lead through action, and by example, as opposed to directing or commanding other people to take action. Often, the achievements of such people transcend political, cultural, and generational boundaries. Unfortunately, such remarkable people often risk their reputations, their livelihood, and, all too often, even their lives.”