The Aryans were not simply invaders, unlike other conquerors; they modified the demographics of the north western region of the Sub-Continent & the culture of most of the region too. Had it not been for them, there would have been no Vedic civilization, neither would there have been any technological advancements as a result of that civilization seeing as the Harappans collapsed due to a variety of factors. We wouldn't even be speaking our current languages if it weren't for them. Keep in mind that a vast majority of people in the north western & to some extent northern regions of the Sub-Continent descend from them, even if some of them no longer resemble them entirely in appearance.
The people who fought against the Greeks in the north western regions of the Sub-Continent were Aryans or the descendants of Indo-Aryans themselves. There was less mixture at that time, so I am guessing the Aryans were still around in their purest forms. King Porus fought bravely against Alexander the Great. In fact, Alexander was so impressed by him that after capturing his kingdom in Punjab, Alexander asked Porus how he would like to be treated. Porus's response was: "the way one king treats another king". It was because of that Alexander the Great returned to him his conquered Kingdom provided they become a protectorate of the Macedonian empire.
By the way, the Greeks were well aware of the Aryan heritage of the Indus. Alexander the Great had even planned an attempt at population dispersion throughout his empire to get the Indo-European tribes to mix up, but he died before being able to accomplish that. The descendants of the Indo-Aryans were the first to resist every invader that tried to enter the Indus. The people of Sindh fought bravely against the Islamic invaders as well, as was their right to do so. We follow Islam today, because we believe in it, similar to how loads of Muslims in your own country follow Islam. By the way, Asoka the Great, as far as I know, descends from Vedic Aryans.