The Fianna are a kind of military Order who are supposed to be devoted to the service of the High King and to the repelling of foreign invaders.
The requirements for joining the Fianna are vigorous. Each man has to know by heart the poet's repertoire, submit to an initiatory test of his skills and courage, including having spears thrown at him, and being able to withdrawn a thorn from his foot while stooping under a low branch and running. Besides warriors, they had druids, physicians and musicians amongst their number. As it was a warband which upheld the country, each man was free of tribal retribution if he killed a member of any family, nor might his own family avenge him if he was killed on active service.
The Fianna are an order of chivalry whose qualifications were even more rigid than those of King Arthur's Round Table. And every man of them was bound to three things, to take no cattle by oppression, not to refuse any man, as to cattle or riches; no one of them to fall back before nine fighting men. And there was no man taken into the Fianna until his tribe and his kindred would give securities for him, that even if they themselves were all killed he would not look for satisfaction for their death. But if he himself would harm others, that harm was not to be avenged on his people.
Maxims of the Fianna
If armed service be thy design, in a great man's household be quiet, be surly in the narrow pass.
Without a fault of his beat not thy hound; until thou hast ascertain her guilt, bring not a charge against thy wife.
In battle meddle not with a buffon, for he is but a fool.
Censure not any if he be of grave repute; stand not up to take part in a brawl; have naught to do with a madman or a wicked one.
Two-thirds of thy gentleness be shown to women and to those who creep on the floor (little children) and to poets, and be not violent to the common people.
Utter not swaggering speech, nor say thou wilt not yield that which is right; it is a shameful thing to speak too stiffly unless that it be feasible to carry out thy words.
So long as though shalt live, thy lord forsake not; neither for gold nor reward in the world abandon one whom thou art pledged to protect.
To a chief do not abuse his people, for that is no work for a man of gentle blood.
Be no tale-bearer, nor utterer of falsehoods; be not talkative nor rashly censorious. Stir not up strife against thee, however good a man thou be.
Be no frequenter of the drinking-house, nor given to carping at the old; meddle not with a man of mean estate.
Dispense thy meat freely; have no niggard for thy familiar.
Force not thyself upon a chief, nor give him cause to speak ill of thee.
Stick to thy gear; hold fast to thy arms till the stern fight with its weapon-glitter be ended.
Be more apt to give than to deny, and follow after gentleness.
Trials and Tests of the Fianna
There were many tests that a prospective member of the Fianna had to pass before being admitted into the order. No one was permitted into the ranks of the Fianna until he passed these trials which showed his worthiness.
The applicant must be versed in the Twelve Books of Poetry, and must themself be able to compose skillful verse in rhyme and meter such as were the masters of Gaelic Poesy.
The applicant must then be buried to their waist in the earth, and then armed with a shield and a hazel stick, defend themselves against nine warriors who would stand around them and cast spears. If the applicant were wounded, he/she failed and was not accepeted.
The applicant's hair was then braided, and the Fians then would chase the applicant through the forest. If at any time the applicant was overcome, or a single braid on his/her head disturbed, or if a dry stick cracked beneath the applicant's foot, he/she then failed and was not accepted.
The applicant must be able to leap over a lath level with his/her brow, to run at full speed under one level with his/her knee, and also be able to draw out a thorn from his/her foot and never slacken speed.
If a man, he must not take a dowry with a wife.
Skills a Fian must learn include all forms of combat and martial arts: sword-mastery, fencing; archery; wrestling; four forms of unarmed combat approximating to judo, karate, kung fu and foot-fighting; boxing; riding; marksmanship with all forms of weapons; tracking; running; spear-throwing.