Kshatriya
The term Kshatriya, or Kshetreya(Kshatr/Kshetra-Field/realm in Sanskrit) refers to the warrior caste in the traditional Indo-Aryan Indian Hindu caste system. The term 'warrior' in this context covers the aristocratic or landowning-ruling classes, including kings.
It is not the intention here to debate whether the infamous Aryan invasion of India ever occured or not but it is certain that The Kshatriya caste is said to be the highest caste in the Aryan hierarchy of society before the Brahmins took over that status.
Earlier in Indo-Aryan Vedic societies, the Rajanyas (Rajan/Raja--King in Sanskrit )or Kshatriyas were the highest caste, as the social framework of those societies or clan depended on the patriarchal supremacy of the King/ruler/Chief as the apex of spiritual and political power.
In those times, The Kshatriya king or Ruler was often aided by a spiritual advisor ( the Brahman/Druid).
In India,The period after the Epic Age or the Later Vedic Age (1000 bc–600 bc) was marked by the rise of numerous small republics and kingdoms,The rising popularity and aspirations of the Brahmin priests began to collide with the authority of the Kshatriyas, who formed the ruling class of each kingdom or republic there began a tussle for supremacy between the Kshatriya nobility and the Brahman clergy in all the Indo-Aryan regions (from Iran to North India).
This is evident in the rise of Kshatriya religions like Zoroastrianism in Persia and Buddhism in North India, which were attempts at overthrowing the pale of priest craft and priestly power in the Vedic fold.
Then the Vedic religions became institutionalized, After the fall of Buddhism in India ,the Vedic religion was 'brahmanised" into Modern-day Hinduism, which accorded the Brahmin priest the highest place in the caste system and in Persia the Vedic religion was 'Kshatriya-ised".. And the rulers/kings were placed on the top.
In Modern India,(Because caste is determined by familial inheritance, actual historical rulers and ruling dynasties are not necessarily of Kshatriya caste, since many obtained power by conquest or other similar means)perhaps the only true Kshatriya castes are the Rajputs of Rajasthan and North India (Raja-put--In Sanskrit--"son of king".)
Some of them claim to have descended from the original Aryan Vedic kshatriyas yet the actual origins of these rajputs are yet being debated. They could also be partly descended from the pagan foreign tribes who poured into the Indian sub-continent from the Oxus and Jakartes region of Central Asia /Eurasia, around the time of the birth of Christ. Viz—The Parthians, The Hepthalites and the Scythians (in Sanskrit—Shaka) These New foreigners entering India, found in Hinduism, the prevalent religion an increasing resemblance to their own animist/pagan beliefs and customs and thus adopted to the culture and traditions of the natives and mingling in their society. It is for some unknown strange reason that these new foreign converts to Hindu society were strongly against buddhism.( it is speculated that by the time ,they entered India,Buddhism had spread across the Eurasian regions and had assimilated or caused the end of the pagan religion there.When the descendants of those same tribes entered India , they found their old traditional foe in the new land and aligned with brahmanical Hinduism (which was closest to their own pagan and sun-worshipping beliefs) against buddhism.
Hence the current Rajput stock of The Indian sub-continent can be said to be hybrid descendants of the earlier Aryan kshatriyas with the later Eurasian and scythian pagans
The Rajput kshatriyas are staunchly Hindu, Martial in spirit, fiercely proud carrying a long history of lineage and tradition,
They are divided into 36 clans consisting of 3 basic lineages, Surya Vansi---Solar Race, Chandra Vansi-- Lunar Race, and Agni Kula-- Fire Born.
The Surya vanshi claim direct descent from the Vedic Sun-God through the Vedic Emperors Ikshvaku and Manu. (Lord Rama of the hindu pantheon and Gautama Buddha , the founder of buddhism are said to be descendants of the solar lineage.)
The Chandra Vanshi claim direct descent from the Vedic Moon-God (Lord krishna of the Hindu pantheon is said to be of the lunar lineage)
The Agnikula clans as per Hindu mythology originated by Hindu Brahmans having creating them through a sacrificial fire for the purpose of defeating demonic forces. (This can probably be interpreted as the baptism of the Eurasian and pagan tribes into hinduism, wherein a vedic fire-ritual was conducted to purify their "unclean' foreign status and make them Kshatriya hindus.The demons here for the brahmans are probably metaphors for the Anti-Caste, Anti-vedic and Anti-Hindu buddhists of those times, who were ,as mentioned earlier, the common foe for the foreigner pagans and hindu brahmans.)
Later on,In the history of India, the Brunt of the Islamic invasions into India during the middle ages was faced by the Rajput clans of Rajasthan who fought fiercely against the Arab and Turkish Islamic invaders to defend their heritage and homeland, often to the very end of their lives and their kingdoms.
Curiously enough,in religious matters, the kshatriyas refuse to accept the supremacy of the Brahmin priest as higher than them on the spiritual platform (as is the custom in the rest of India) and some scions of their noble families even officiate as priests in their Hindu temples.(E.g. --The Regent of the Rajput House of Mewar is also the high priest of his clan deity--the form of Shiva known as "Ekling ji”.) This could be a throwback to a distant traditional memory of ancient vedic India where the Kings were worshipped as God's own representatives in the world and were supposed to have a direct kinship with them.
Sikhism --the recent egalitarian warrior religion of North India started by the mystic seer Guru nanak in the 16th century and perfected by nine subsequent gurus is also seen to be modelled on the Ancient mystical kshatriya-warrior ethic of the Vedic Hindus.
There are also some other Kshatriya communities in India such as the Marathas,Kunbis, Kurmis,Jats etc. They were basically members of other agrarian and serf communities baptized as warriors by Hindu kings to supplement their armies. (Neo-kshatriyas). However they are not considered to be part of the kshatriya fold by the rajputs.
Rajput power finally ended in the 17th-18th century after the last surviving kingdoms were either defeated or became vassals to the British empire of India.
Today apart from Rajasthan, Rajputs, their clans and their descendants are found all over India.Some rajputs also converted to the faith of sikhism during the time of the Sikh Guru ,Guru Gobind Singh.There are also some clans of Rajputs who are converts to Islam and are now mainly found in Pakistan.
Rajputs are known for their sense of honour, chivalry and love of tradition and revelry. They celebrate weddings, festivals and feasts to the Gods with great enthusiasm ,customs which are now fading against the scenario of Indian culture which is now being rapidly urbanised and modernised.
Most of these Rajputs are tall, relatively fairer skinned than the other communities and have sharp grecian/mediterranean/caucasian features hinting at a definite Aryan /Scythic descent.