While deployed in Iraq in 2010 as a combat medic, Marks got injured in both her hips. She later had to have three operations and took up swimming a year later. In 2012, she was accepted into the US Army World Class Athlete Program (WCAP) and found fit for duty to continue being a soldier in the Army.
In 2014, while in London for the Invictus Games — the international sporting competition Prince Harry founded for injured, sick, or wounded service personnel — she fell severely ill with a severe respiratory infection and had to be put on life support. She now lives with reduced lung capacity and vision impairments as a result. Marks credits the doctors at Papworth Hospital in Great Britain for saving her life; at the Invictus Games in 2016, she gave one of her medals to Prince Harry to give to Papworth Hospital. In 2017, she underwent an amputation of her left leg below the knee.
