Bernard Lewis says Islam imposes, without limit of time or space, the duty to subjugate non-Muslims

The renowned historian of Islam and the Middle East writes on p. 73 of The Political Language of Islam:

"...it is the duty of those who have accepted them [Allah's word and message] to strive unceasingly to convert or at least to subjugate those who have not. This obligation is without limit of time or space. It must continue until the whole world has either accepted the Islamic faith or submitted to the power of the Islamic state.”