It was a suicidal blunder that the Muslim rulers neglected to build a naval force. They remained uninterested to the potentialities of sea power. They paid their attention to the defence of the passes of the north-west, as these were the historic routes followed by every invader including themselves to enter subcontinent.
The Muslim rulers could not think that their empire would fall to the naval strength of the European merchant communities. The activities of the Portuguese in the latter part of the sixteenth century failed to act as an eye-opener for the Muslim rulers.
Even in the time of a powerful emperor like Akbar, the Portuguese looted Muslim merchants and even the pilgrim ships. They raided coastal territories in Bengal in the reigns of Jahangir and Shah Jahan. These incidents clearly showed the approaching danger.