One thing we have to understand is that invasions are a central part of our history. Throughout our long history, we invaded and we were invaded. Same for most other ancient civilizations. Invasions are like pollination in agriculture. This is how ideas spread and cultures grow.
Let me first disabuse you of the notion that India has never invaded. India has often extended soft power (and sometimes hard power) over rest of Asia.
India's Invasions:
- We invaded most of Asia with our religion, Buddhism. Emperor Ashoka and many other emperors tried hard to spread our religion and it worked. At some point, Buddhism covered a big chunk of Asia from Afghanistan to Japan.
- When you go to Bali or Cambodia, you might wonder why are Hindu temples all over. Thai emperors are named Rama (Kings of Thailand) and Indonesia's (Sri Vijaya) symbol is Garuda. Ramayana is embedded in various local cultures. Singapore is a Sanskrit word: Singa+Pura (Lion city). From the Isan province of Thailand to the Shaolin school of China (possibly founded by a South Indian monk, Bodhidharma) to Zen of Japan (from the Sanskrit word Dhyan), India has its cultural invasion all over.
- India didn't merely invaded culturally. Sri Lanka was often ruled by kings from Tamil Nadu. Chola territories extended all over South East Asia. They had trade routes that go all the way to China.
- In the north, Chandragupta Maurya invaded Afghanistan and ruled parts of Iran and Burma.
- Under Emperor Kaniska we ruled Uzbekistan, Tajikistan among other parts of Central Asia.
- Under Mughals, our territories often included Afghanistan and sometimes as far as Central Asia. Here is the picture of Mughals capturing Kandhahar.
- The Sikh empire captured Ladakh (was a part of Tibet until then) to add with Kashmir and had defeated Afghanistan.
In short, Indians invaded quite a bit.
Think about our invaders.
- Emperor Kanishka, among India's great emperors, was an invader. He was part-Greek, part-Iranian and part-Afghan. He issued coins in Greek.
- If Aryan invasion hypotheses is true, probably most of Indian kings were descendents of invaders. However, we don't really know how, when and if the invasion happened.
- And this is a work of an "invader".
History of India is complex. It was not like we were all one people and suddenly the Islamic invaders came and destroyed everything. Throughout our ancient history, India was the center of invasions (both inbound and outbound). These invasions often brought new ideas and substantially enriched our culture. In music, architecture and dance, we got richer with each invasion. From the Tomatoes we eat to Tea we drink to Silk we wear to English we write to Taj Mahal we cherish, it was all work of "invaders".
In summary, if there were no invasions, our culture would have sucked. That said, we would have been better off without some of the invaders (such as Timur the lang, the plunderer of Delhi, Nadir Shah who stole our major treasures, Mahmud of Ghazni - the barbarian who plundered big chunk of India and the Portuguese who destroyed precious Hindu temples such as Konark and Mylapore Kapaleeswarar in Chennai)