Qutb al - Din Aibak, a former Turkic Mamluk slave of Muhammad Ghori, was the first sultan of Delhi, and his Mamluk dynasty conquered large areas of northern India. Afterwards, the Khalji dynasty was also able to conquer most of central India, but both failed to conquer the whole of the Indian subcontinent. The sultanate reached the peak of its geographical reach during the Tughlaq dynasty, occupying most of the Indian subcontinent. This was followed by decline due to Hindu reconquests, states such as the Vijayanagara Empire asserting independence, and new Muslim sultanates such as the Bengal Sultanate breaking off.
who made delhi the capital of his kingdom for the first time
Qutb al - Din Aibak