"invasion"?

[Arun Gupta]

Elst's book "Update on the Aryan Invasion Debate" is available on-line,
at http://www.voi.org/books/ait/

so it is possible to check what debate is meant.

As Rohan Oberoi pointed out, the debate is political in nature;

http://www.voi.org/books/ait/ch12.htm

discusses Elst's view of the political debate in India.

The debate was hardly over three decades ago, if, as quoted by Elst,
in 1991 a ex-member of Parliament could write "Sanskrit should be deleted
from the Eighth Schedule of the Constitution because it is a foreign
language brought to the country by foreign invaders - the Aryans."

-Arun Gupta