When Shah Jahan became ill in 1658, Dara Shukoh (Mumtaz Mahal's eldest son) assumed the role of regent in his father's stead, which swiftly incurred the animosity of his brothers. Upon learning of his assumption of the regency, his younger brothers, Shuja, Viceroy of Bengal, and Murad Baksh, Viceroy of Gujarat, declared their independence, and marched upon Agra in order to claim their riches. Aurangzeb, the third son, and ablest of the brothers, gathered a well trained army and became its chief commander. He faced Dara's army near Agra and defeated him during the Battle of Samugarh. Although Shah Jahan fully recovered from his illness, Aurangzeb declared him incompetent to rule and put him under house arrest in Agra Fort.