The medieval Turkic empires were built on horse-warrior economies in a very militarized society. The horse was the tank of the medieval world & the Turk was its master. Al-Jāhiz said an average Turk would spend more time on horseback in his life than on foot.
Eurasian nomads like the Turks used horses for everything (meat, fat, milk, hide, carriage, transport, etc). Every Turk male on the steppe was trained as a horse archer from age of 3-4 yrs old. This meant the nomads always had an elite cavalry ready by mere virtue of existing.
This gave Eurasian nomads a decisive military superiority over sedentary settled civilizations like India & China in the pre-gunpower medieval era. The mastery of the Turks as horse archers was admitted by the Arabs & Persians too. They could shoot 6 arrows in 60 seconds on horseback.
There was unanimous consensus among Islamic writers that the Turks were militarily superior due to their horse archery. Ibn Khaldun said “Thanks to these virile virtues - [they are] the saviors of Islam”. Al-Jāhiz said, “Nothing can oppose the Turks. None can withstand them.”
We see a general pattern is being established now. What was the status of horses & cavalry in Hindu India? Hindus had been using horses for a long time. They made a “science of horses” to classify them based on anatomy, breed, age, etc. (aśvaśāstra-s)
In India, heavy cavalry-mounted shock combat never took hold due to the role of elephants as formation breakers. We had light 1-handed lances. The other flaw was horse-mounted archery was never developed. Archery was left to the infantry. A similar weakness existed in the Byzantine Empire.
The next major issue was India was one of the worst places on Earth to rear horses & maintain them. There was a problem with both the quality & quantity of horses available. The climate was too hot, there was little grazing grassland & there was too much disease due to the tropics.
A similar situation existed in China too. This is why China was also overrun by horse-warrior Eurasian nomads. One reason why good quality pasture land wasn't available was bc sedentary agriculture occupied most good land. Direct competition of horse-breeding vs arable farming.
On the other hand, the best lands to raise horses were in Central Asia, Iran & Arabia. Indians imported “Turki” & “Bahri” horses. (from land & sea). Marco Polo said there is no ship that goes from the Persian Gulf to India that isn't loaded with horses.
The horses that were imported used to die very quickly, this was again noted by Marco Polo who said “great wealth of Indian kings is wasted in buying horses”. Hence, it is not much surprise that great skills in horse-mounted archery were not developed. It was the domain of Turks. The Turks & other Eurasian nomads of the steppe on the other hand had had 3000+ years to perfect the art of horseback riding & mounted archery. They had a monopoly over it. Al-Jāhiz said the Turks could send 10 arrows at full-gallop before the Arab could send even one.
By the Ghaznavid era, the Turks had developed an army core of heavy cavalry + light cavalry archer flanks. These armies were more mobile than any infantry & could carry out decisive quick charges on the battlefield. The Turk armies were mostly comprised of professional soldiers too.
Turkic superiority in conquest had been rightfully noted. Sultan Balban joked he could slaughter an army of 100,000 Hindu ranas & rais with just 5000 Turk horsemen. The 2nd Battle of Tarain was decided by just 10,000 mounted archers according to Firishta.
Hindu texts of the 12th century had started noticing the military superiority of the Turks too. The प्रबन्धचिन्तामणि says the King Jayachandra was “the cripple” & when he heard the mleccha [Turks] his mind was bewildered & he plunged his elephant into the river.
The Turks additionally had cut off the supply routes of horses for the Hindus. (War-horse diplomacy). The only power of the Hindu (the war elephant) had proven to be of little use in front of the horse-warriors of the Eurasian steppes. Hence, The Gates of Hind was opened.
All this should make one thing clear. Hindus did not lose to the Turks because of “caste disunity, ethnic disunity, lack of national consciousness or feudalism” or any other ahistorical reason. Hindus lost because the Turks were militarily superior. They would always have won. To put this into perspective, we must look at Song China has posted below. It was a huge unified bureaucratic empire that collapsed in front of steppe nomads like Jin. What chance did Chauhans or Hindu Shahis ever have?
Now, it should be clear that the Hindu kings who fought the Turks (Jayapala, Jayachandra, etc) were great men who tried their best. They did all they could. They still lost. That is alright. However, the quack notions that they “betrayed each other” should be let go of.
This quack and ahistorical narrative of trying to find “deeper reasons” for Hindu defeat has led to the spawning of many unsubstantiated theories.. from lack of unity to caste-oppressed feudalism squashing fighting spirit et al. Hinduism is blamed for simple lack of horses.