I am doing research on the Northern Crusades specifically, so my question mainly pertains to the Teutonic Order; I know they drew heavily from the Knights Templar for their early guidelines so there may be some overlap.
The concept of Halbbrüder and Schwertbrüder, juxtaposed against ‘full’ Ritterbrüder is really interesting to me but I can’t find much on whether there was a progression one would usually take. For instance, the Schwertbrüder were simply coopted from the Livonian Order after their defeat at Saule; was there a stigma among the Teutonic Knights for these men? Did they tend to seek a “transfer” of sorts? Was this done at all?
Another example I’m interested in: say you’re a German from Lübeck who answers the call to settle eastward. For the sake of argument let’s say you’re from a minor noble family and you’re at least somewhat literate. You decide you want to join the Crusade to make a name for yourself and help spread Christianity. What route do you take and what is the equivalent of “career planning” involved?
Or is that an entirely anachronistic way to approach the question?
I believe that terminology got mixed up a bit. The 'Schwertbrüder' (eng. Sword Brethren) was the common name of the Order of the Livonian Brothers of the Sword (Fratres militiae Christi Livoniae), much like members of the Poor Fellow Soldiers of Christ and Temple of Solomon were called 'Templars' and members of Order of Brothers of the German House of Saint Mary were called 'German Knights' or, chiefly in Poland, 'Crossmen' due to their distinctive emblem. Sword Brethren merged with aforementioned German Order in 1237, as the defeat in he battle of Saule and death of Grandmaster Volquin crippled the Order and made any further success hardly possible, especially given that Sword Brethren were deeply conflicted with bishop of Riga that was their nominal superior and Danish king Valdemar II who had claims to conquered territories in what is now Estonia. At the same time, German Order enjoyed rapid development and was backed directly by the Emperor and the Pope. This means that the decision of the union was very sound politically, especially given that the Livonian branch of the German Order Sword Brethren were transformed into retained some administrative independence. This also suggests that German Order kept them in high regard, treating them as valuable assets.
Now, the 'strata' knightly orders like Templars, Joannites, Hospitallers of Teutons were pretty much separate organisation with little to no mobility between them not unlike the strata of the medieval society. Brothers ('brothers knights' or 'full brothers') were almost exclusively knights, usually landed nobles or even aristocrats who formed the core of the order and were responsible for military command and administration. 'Order servants' (ger. Knechten) also known as 'sergeants' were either poorer knights or commoners who formed the bulk of the military forces and were, for all intents and purposes, professional soldiers. Division between knight brothers and sergeants was not unlike the division between officers and enlisted men in 19th century armies. They formed two distinctive corps and while promotions of the commoners to the officer positions were not unheard of, they were usually very rare and limited to exceptional circumstances, so they could not be considered a viable option of military career for a lowly soldier. Then were the chaplains, recruited from the members of clergy who performed ecclesiastical and clerical duties. The term 'half-brother' (ger. Halbbrüder) was an rough equivalent of a 'honorary member' and reserved for people (usually lay commoners) who neither were knights nor participated in the military actions of the Order, but were offering financial or political assistance or rare skills, usually related to administration or engineering. A 'civilian service' practice in many armies is a good modern equivalent.
Replying to the second question, it was precisely the route many younger German knights took. Even joining as a common knight, bringing to the Order little more than oneself, horse, arms and basic retinue could have been profitable, as the fast development of the Teutonic Order in southeastern Baltic area meant that new forts, castles and commanderies were being established quite often, and thus the ambitious and skillful knight could have been promoted to an administrative position in such place and sooner or later gain the position of a local commander (ger. Komtur) that was opening the possibility of attaining higher positions within the Order. Such advancement must have been common, as according to Alexander von der Oelsnitz, out of first 35 Grandmasters of the German Order (from Heinrich Walpot to Johann von Tiefen) only 2 came from aristocratic houses, 11 were sons of rich feudal lords and remaining 22 came from relatively unknown knightly families.
Summing it up, all knights were usually admitted as 'knight brothers' (the highest caste within the Order) and the promotion meant receiving practical managerial duties, usually related to the military command or the organisation of the monastic life. Usually, such knight could count on getting a rank of Procurator (an officer, not related to judicial title), then local commander, then a bailiff and then, with enough luck and skill, one of three Landskomturs (each overseeing all bailiwicks in Germany, Prussia and Livonia) or even that of Grandmaster himself, not counting the unofficial positions within the Order, increasing chances of being selected for the position of one's superior should it became vacant.