The training regimen of the Ottawa Medieval Sword Guild is based on the writings of Fiore dei Liberi, an Italian fighting master from the second half of the fourteenth century. His system of combat, which he called "The Flower of Battle" (Fior di Battaglia in Italian or Flos Duellatorum in Latin), is a description of fighting techniques he had learned and developed in over 50 years as a warrior. Written in the early fifteenth century, his treatise survives in three slightly different versions.

The most complete of these manuscripts is the version owned by the J. Paul Getty Museum in Los Angeles. Known as the Getty version, it contains fairly lengthy explanatory notes and descriptions for each plate. Because of its completeness and amount of material, this version is the primary source text for many practitioners of Flos Duellatorum.

The most easily accessible version comes from a facsimile made by Francesco Novati of a manuscript held by the Pisani-Dossi family in Italy. The Pisani-Dossi version (sometimes referred to as the Novati version) contains similar plates to the Getty version, but with shorter rhyming couplets explaining each plate.

The Morgan version, so-named for the J.P. Morgan Library which owns it, is the third known version of the manuscript. This manuscript contains the expanded text descriptions similar to the Getty version, but the text is structured differently, and is incomplete, missing information on close-quarter (wrestling and dagger) fighting.

Flos Duellatorum is divided into several sections, corresponding to different weapons. This includes grappling, dagger, the sword wielded with one hand, the sword wielded with two hands, the sword in armour, spear, pole-axe, and even mounted combat. What makes Fiore dei Liberi a good source of information is the consistency of his system. Within these different sections, positions, guards and techniques are repeated, often with variations individual to the weapon in question. These different sections combine to form a comprehensive fighting system, where patterns and techniques in one section closely mirror corresponding techniques in others. Practitioners of dei Liberi’s art learn a system of fighting, rather than how to fight with a number of different weapons.

The three extant copies of Fiore dei Liberi’s manuscript do not follow the same format or order of presentation. Both the Getty and the Pisani-Dossi versions of the manuscript begin with unarmed combat and move on to ever more complex weapons and wider distances of combat, culminating in mounted combat. This organization is generally considered a good pedagogical approach, starting with simple techniques without weapons and then building upon what the student already knows.

The Morgan manuscript, on the other hand, reverses the order of the sections in the manuscript (there are small exceptions, such as the order of the different types of mounted combat or the wrestling and dagger sections). The Morgan manuscript thus presents the material as one would fight a structured duel, beginning with passes on horse, followed by spear and poleaxe in armour, the sword, and finally the wrestling and dagger. This organization seems to be based more on a logical presentation of the techniques, but not necessarily the best order in which to teach them.

In addition to differences in organization, there are substantive differences in the amount of information contained in each manuscript. The Pisani-Dossi manuscript, which has been the most widely circulated, contains the least text of the three manuscripts, with most illustrations accompanied by a short couplet of explanatory verse. The Getty and Morgan include longer paragraphs of text which generally go into more technical detail in terms of movement and footwork. The Morgan manuscript as it survives is incomplete, however, and does not include, among other things, the wrestling or dagger sections seen in the other two (though they are referred to in the introduction).

In the past, the OMSG Training program has been developed primarily with the Pisani-Dossi manuscript, which has been available online in the form of a number of facsimiles transcriptions and English translations. Over the past couple of years, different individuals and groups, to the benefit of the WMA community, have been translating the Getty and Morgan manuscripts. Currently, there are a number of different sources of information and several on-line translations are in progress. The OMSG training program is based on in-house research and development, supplemented by on-line discussion groups, forums, published interpretations, and direct links to others in the WMA community.

As discussed above, these sources do not merely represent a "swordfighting manual", but a comprehensive multi-weapon fighting system where different sections combine to form a comprehensive whole and patterns and techniques in one section closely mirror corresponding techniques in others. Because of this, members of OMSG do not practice exclusively with any one weapon or only those weapons they wish to become proficient in. Indeed, a given training session may include several different weapons, each doing virtually the same technique, adapted for different situations.

One important aspect of Flos Duellatorum is the necessity of understanding the different levels of technique in the manuscript. Different techniques have different purposes, and would be used at a different point in an engagement. Some techniques illustrate an attack, others demonstrate a defence, still others show how to counter the defensive technique, and so on. Instruction in OMSG is designed to teach fighting techniques, but also fighting concepts and how to recognize recurring themes or situations in the system, as well as how a single technique can lead to multiple applications.

OMSG training includes, but is not limited to:

In practise, wrestling is generally the conclusion of a fight when two opponents close to the point that weapons become more of a hindrance than an aid. In training it provides foundational skills that help form the basis from which the rest of the system is structured. Although other sections of the manuscript also include demonstrations of how to take ones opponent to the ground, the wrestling section illustrates the four basic guards from which all wrestling techniques are based, as well as techniques performed between unarmed opponents.

The dagger section is the longest in the treatise and is probably the most important. Fiore dei Liberi himself states that more than any other, the dagger techniques are the most lethal techniques and encounters with the dagger most often end in death. The dagger section also shows the widest variety of arm-locks, disarms, and takedowns that one finds referenced throughout the rest of the text. These techniques are designed for a variety of situations including an unarmed Master defending himself against an attacker armed with a dagger, two opponents armed with daggers facing off, and techniques that dei Liberi recommends be used in armour. Besides defending against attacks, the dagger section also includes the largest collection of contrary techniques where the attacker overcomes the defensive technique previously described.

The sword is the weapon most people identify with medieval combat and is covered in depth in the text. The type of sword illustrated and used almost exclusively by dei Liberi is a hand-and-a-half sword that can be wielded either with one or two hands. As opposed to the cutting and parrying that one might see in movies, the text tends to stress a quick combat, where a single cover and counter strike or thrust would be decisive. In addition, besides ‘bladework’, dei Liberi also teaches a large numbers of sword grabs, wraps, grappling, and takedowns (many of which are directly related to previous wrestling and dagger techniques).

An additional set of techniques, which are central to much of what OMSG does, is the sword in armour. Adding to the previous sword techniques, these techniques are designed specifically for fighting in harness. Most of these techniques involve close-in fighting, where the sword is held with one hand on the grip, as normal, and one hand griping the blade at the mid-point. This method of gripping the sword, often called "half-sword", allows more control and leverage in putting the point of the sword into the gaps in an opponent’s armour.

The poleaxe is a specialized weapon designed to defeat the plate armour of the late fourteenth and fifteenth centuries. It consists of some combination of hammer-head and spikes on a 5 to 6 foot wooden shaft. The poleaxe section resembles a combination of the sword in two hands, as well as including sword in armour (i.e. half-sword) techniques These techniques are designed to deliver powerful blows, and higher tempo training/sparring is conducted only in full plate and maille armour.

Although the sword holds the top spot in popular myth, the spear was probably the most common weapon on the medieval battlefield and has been used in one form or another for thousands of years. In the context of a formal duel between two men-at-arms, the spear would often be the primary weapon. The spear techniques in the treatise cover a variety of crossings from both the left and right side (the first time in the system where similar techniques are shown from both sides).

Although not normally a part of everyday instruction, several members of the OMSG study and train the mounted techniques of Flos Duellatorum. One should also note that many aspects of mounted combat described by dei Liberi have application to other aspects of the art and must be included in any complete study of the manuscript. These cover a variety of situations including horsemen facing off with lances, swords, and unarmed. Rather than the formal joust of the later Middle Ages, the mounted combat in the treatise includes attacks, covers, disarms, and unmounting techniques to provide a more rounded system of fighting from horseback. For more information on mounted combat instruction, see Chris Kovach Equestrian Martial Arts.

Besides specific sections dealing with a variety of weapons employed by the medieval man-at-arms, there are a number of special, situational techniques. Besides equal matches of two fighters, as would take place in a formal duel, these techniques cover situations of self-defence, where a person defends themself with a mismatched or even improvised weapon. Included in these techniques are sword versus dagger techniques, sword versus thrown weapons, individuals facing multiple opponents, two clubs and a dagger against the spear, and defences against a dagger attacking using a stick or cloth cap. These techniques are still based on the same basic system of defence, and provide a fun change of pace to regular training, as well as an insight into the versatility of the system.