Vanadhi
That's news to me. From what I understand, there were never any wars b/w Vaishnavs & Shaivyas - in fact, if Buddhism & Jainism could be introduced and prosper until the 11th century (during the Muslim invasions), then why would there be wars b/w Vaishnav & Shaivyas? Yeah, different sects competed for royal patronage in various kingdoms, but different members of families practiced different religions. E.g. In Thaneshwar, Rajyavardhan was a Buddhist whereas Harshavardhan, his brother, was a Shaivya. Among the Mauryas, Chandragupta, towards the end of his life, embraced Jainism, while Ashoka embraced Buddhism.
Yeah, in classical age India (i.e. India b4 1000AD), there were wars b/w different kingdoms, but were any of them on account of Vaishnav vs Shaivya beliefs of the battling dynasties/kingdoms?
In the 12th century that you're referring to, the South was beginning to be attacked by the Muslims who had overrun the North, and most of that destruction happened @ the hands of the Bahmani sultans and beyond, just like the Ghaznavis, Ghoris, Mamluks, Khiljis and Tughluqs had done in the North, and the Syeds, Lodis and Moghuls would continue.