Ksatriya

Also spelled ksatriya, second highest in status of the four varnas, traditionally the military or ruling class. Ksatriya means holder of ksatra (authority). In modern times, the ksatriya varna is held to include a broad class of caste groups, differing considerably in status and headed by the aristocratic Rajput lineages.
(Brittanica CD. Version 97. Encyclopaedia Brittanica Inc., 1997)

Dharma teaches us to be nonviolent but to defend dharma and ourselves when attacked.
In Mahabharata, Virata Parva, Arjuna says to prince Bhuminjaya (acting as his charioteer) before fighting with Kauravas near the city of king Virata: "The one with the emblem of a golden waterpot on his flagstaff is Drona [Arjuna's guru in martial arts]. I always worship him. You should circumambulate his chariot and I will strike him only if he first attacks me, for such is the duty of kshatriyas." (translation by Krishna Dharma)

Motto of U.S. special warfare units is "De oppresso liber" (Liberating the oppresed). This is ksatriya's task. Real liberators are actually Vaishnavas because they liberate everyone from the oppression of maya, illusion.

Quotes: Brahmana

"Considering your specific duty as a ksatriya, you should know that there is no better engagement for you than fighting on religious principles; and so there is no need for hesitation."
(BG 2.31)

"Ksat means hurt. One who gives protection from harm is called ksatriya (trayate - to give protection)." (BG 2.31p.)

"O Partha, happy are the ksatriyas to whom such fighting opportunities come unsought, opening for them the doors of the heavenly planets." (BG 2.32)

[Sage Parasara Muni:] "The ksatriya's duty is to protect the citizens from all kinds of difficulties, and for that reason he has to apply violence in suitable cases for law and order. Therefore he has to conquer the soldiers of inimical kings, and thus, with religious principles, he should rule over the world." (BG 2.32p.)

"Heroism, power, determination, resourcefulness, courage in battle, generosity and leadership are the natural qualities of work for the ksatriyas."
(BG 18.43)

[Maharaja Pariksit to Kali:] "Oh, who are you? You appear to be strong and yet you dare kill, within my protection, those who are helpless! By your dress you pose yourself to be a godly man [king], but by your deeds you are opposing the principles of the twice-born ksatriyas."
(SB 1.17.5)

"When the ruling administrators, who are known as the ksatriyas, turned astray from the path of the Absolute Truth, being desirous to suffer in hell, the Lord, in His incarnation as the sage Parasurama, uprooted those unwanted kings, who appeared as the thorns of the earth. Thus He thrice seven times uprooted the ksatriyas with His keenly sharpened chopper."
(SB 2.7.22)

"Thereafter the power of protection was generated from the arms of the gigantic virat form, and in relation to such power the ksatriyas also came into existence by following the ksatriya principle of protecting society from the disturbance of thieves and miscreants."
(SB 3.6.31)

"If you [the emperor] did not mount your victorious jeweled chariot, whose mere presence threatens culprits, if you did not produce fierce sounds by the twanging of your bow, and if you did not roam about the world like the brilliant sun, leading a huge army whose trampling feet cause the globe of the earth to tremble, then all the moral laws governing the varnas and asramas created by the Lord Himself would be broken by the rogues and rascals."
(SB 3.21.52-54)

"The king is supposed to be pious in whose state and cities the general populace strictly observes the system of eight social orders of varna and asrama, and where all citizens engage in worshiping the Supreme Personality of Godhead by their particular occupations."
(SB 4.14.18)

"Since only a person who is completely educated according to the principles of Vedic knowledge deserves to be commander-in-chief, ruler of the state, the first to chastise and the proprietor of the whole planet, Prthu Maharaja offered everything to the Kumaras."
(SB 4.22.45)

"Although Lord Rsabhadeva knew everything about confidential Vedic knowledge, which includes information about all types of occupational duties, He still maintained Himself as a ksatriya and followed the instructions of the brahmanas as they related to mind control, sense control, tolerance and so forth. Thus He ruled the people according to the system of varnasrama-dharma, which enjoins that the brahmanas instruct the ksatriyas and the ksatriyas administer to the state through the vaisyas and sudras."
(SB 5.4.16)

"Except in a time of emergency, lower persons should not accept the occupational duties of those who are higher. When there is such an emergency, of course, everyone but the ksatriya may accept the means of livelihood of others."
(SB 7.11.17)

"To be influential in battle, unconquerable, patient, challenging and charitable, to control the bodily necessities, to be forgiving, to be attached to the brahminical nature and to be always jolly and truthful--these are the symptoms of the ksatriya."
(SB 7.11.22)

"Being pleased by the full surrender and submission of Lord Bharata, Lord Ramacandra then accepted the throne of the state. He cared for the citizens exactly like a father, and the citizens, being fully engaged in their occupational duties of varna and asrama, accepted Him as their father."
(SB 9.10.50)

"Lord Ramacandra took a vow to accept only one wife and have no connection with any other women. He was a saintly king, and everything in His character was good, untinged by qualities like anger. He taught good behavior for everyone, especially for householders, in terms of varnasrama-dharma. Thus He taught the general public by His personal activities."
(SB 9.10.54)