Zoroastrian King Cyrus the Great in the Bible - liberation of 40k Jews:
King Cyrus allows Return of Jews from Iran to Israel
In the first year of Cyrus king of Persia, in order to fulfill the word of the LORD spoken by Jeremiah, the LORD moved the heart of Cyrus king of Persia to make a proclamation throughout his realm and to put it in writing:
"This is what Cyrus king of Persia says: "`The LORD, the God of heaven, has given me all the kingdoms of the earth and he has appointed me to build a temple for him at Jerusalem in Judah. Anyone of his people among you--may the LORD his God be with him, and let him go up.'" 2 Chronicles 36:22-23
The oppressive forces of Islam acting in both India and Persia circa the middle ages were so much similar, yet the outcome is so drastically different. I mean, if there were any people who had reasons to convert, the Indians probably had more, especially in light of the "caste" problem, that so many profess here as a "particularly rampant" problem (I do not disagree casteism is an evil, but differ in opinion with respect to its extent). Anyway, as a pragmatist, I am open for revision of my views.
It is sad that the Persians wrongly saw Islam as means of Deliverance, rather than the other faiths that they must have been aware of around the time.