Progress to Fighter (sage ability)
Progress to Fighter is an authority-status sage ability, in the study of Instruction, granting the character the ability to transform non-levelled soldiers into 1st-level fighter characters, with commensurate hit points, attack dice, weapon proficiencies and sage abilities. Similar to the ability to train a soldier, the instructor initialises the training with a physical regimen, followed by lengthy and patient instruction in which some part of the instructor's knowledge is passed along. To partake in this instruction, the student must be a soldier, and must have accumulated 1,500 experience.
A natural limitation exists in that the character can only teach what they personally know. For example, a thief with this instruction skill, gained through jack-of-all-trades, could not actually teach the proficiency of weapons beyond what the thief possesses. True enough, the soldier already has proficiencies, which can then be continued along. Further, it assumes the character doing the training already has a THAC0 better than 20, which is what the first-level fighter would have at the end of training. Hit points, on the other hand, are not so limited; the soldier would add 1d10 following the training, regardless of the actual class of the trainer. Sage abilities are of course another element, but they are covered separately, below.
Physical Training
This can be stated rather simply. The student spends two weeks in general physical activity, which does little more than repeat their original soldier's training in a more compress, precise manner. The student is, in effect, merely shown their mistakes, taught to avoid their bad habits, corrected in their stance, speed, approach into melee and so on, with an understand that as a soldier, the character already knows how to do all these things — just not quite well enough to be counted as a levelled fighter. At the end of this part of the training, the student gains 1 hit point, regardless of whether or not they continue in their training.
Thereafter, an additional week is given for each of the four weapons to be used, starting with those the soldier already employs. Already, prior to training, the soldier's THAC0 with known weapons is already 20, but the re-training has to occur anyway, so that the student understands better how to improve their THAC0 with it as they reach 2nd level and up. With unfamiliar weapons, following a week, the student ceases to suffer a proficiency penalty, so that they are able to use these as well as their former fighting tools. Once this part of the training is completed, the student rolls a d10, subtracts 1 (for the 1 previously gained above) and adds that total to their maximum hit points. Again, this takes place whether or not the character continues with their training. At this point, the character is considered to be "1st level," and can be sent into battle as one... but the opportunity to learn sage abilities would have to still be learned sometime in the future. This, though, explains why so many classed fighters in the game setting are quite ignorant.
Teaching Sage Abilities
Regardless of the instructors possessed abilities, the character cannot learn knowledge about any sage study that does not strictly exist as something a fighter would know. A thief instructor might understand, for example, the study of Guile, but since the soldier trying to be a fighter has never personally had any experience from a young age with being a thief, and is in fact older than 10 or 11, there's no possibility of the character emulating what's being taught.
The instructor, not the student, decides what sage field is focused upon, and specifically what study is also. The student has no say about this. If the instructor is a fighter, then it is fairly certain the instructor will have more enough knowledge points in all the sage fields to provide the usual smattering of sage abilities that a player character fighter would start with. It is important to note that non-player characters do not start with 12 pts. in their "chosen" study, but a d12, which might conceivably be a 1 rolled. This merely represents the kind of student the individual is, and does not necessarily reflect on the teacher.