Mahmud's descendants continued to rule over a gradually diminishing empire until 1150, when 'Ala'-ud-Din Husayn of Ghur, a mountain-locked region in central Afghanistan, sacked Ghazna and drove the last Ghaznavid out to India. 'Ala'-ud-Din's nephew, Mu'izz-ud-Din Muhammad, known as Muhammad of Ghur, first invaded India in 1175. After his death in 1206, his general, Qutb-ud-Din Aybak, became the sultan of Delhi.