Kimberley Taylor left the UK to join the Women's Protection Units (YPJ), the all-female affiliate army of the People's Protection Units (YPG) of Syrian Kurdistan, in March 2016.
She travelled to the frontline in Syria in October last year and has been involved in the push to re-take Raqqa, the de facto capital of the dreaded terror group.
"I'm willing to give my life for this," she told the 'Guardian' in a phone interview from the frontline base.
"It's for the whole world, for humanity and all oppressed people, everywhere. It's not just [ISIS] killing and raping. It's its systematic mental and physical torture on a scale we can't imagine," she said.
Taylor hails from Blackburn in the north west of England and studied Maths at the University of Liverpool.
She told the newspaper in the interview published yesterday about her extensive travels across Africa, South America and Europe and how she became involved in political activism working as a writer for left-wing magazines and websites.
Her journey to Syria began during a trip 18 months ago to report for a friend's humanitarian website.
"The lack of food, medicine, shelter, would have been hard enough for any human to endure. In that moment, I made a promise to myself that I would commit my life to helping these people," she recalled.
Taylor is one of an estimated 50-80 British citizens who have travelled to Syria or Iraq to fight against ISIS since 2014.
They join either the People's Protection Units (YPG) of northern Syria, or the Kurdish Peshmerga of Iraqi Kurdistan.