Leadership has always been the backbone of any society, whether fictional or otherwise. Without leaders, there are no armies, there are no organizations, there are no societies. In short, without leaders, there is no advancement. If this applies to the real world, then certainly it applies to Graal.
Since the birth of Graal Militaries, there has always been a major leader figure. In the case of Imperia, this figure was Auel, then Xinke in later years. In the case of the State, it was always Auel. In the case of the Bacseys, it was Harau. No matter the time of its birth or the context of its creation, the glue that binds the members together was that leader. In Imperia, if a feud occurred between two commanders, it was Auel (or Xinke) that made sure that feud did not grow out of proportions. In the State, when commanding officers quarreled, it was Auel that made sure the situation did not get out of hand. Similarly, Harau made sure his Bacseys did not kill each other, but instead focused on their enemies.
You may be thinking that there are many more leaders that appeared over the last five years. The definition of leader in this case is an individual capable of making a society without making it an entity meant to destroy another. For example, the Magnus Imperia was made to unite militaries and not to fight the State. However, Bavaria was made to fight the State. Without the State, there would have been no Bavaria. Thus, its leadership was reliant on the dissent for the State.
Now, you may wonder why these great leaders are so rare. In fact, only 3 great leaders would have appeared over the last 5 years. The answer is simple: its not easy.
First of all, there is the raw charisma required to single handedly make a guild and bring people to work under you. Many people in the military world are very greedy about power, and love having control over others. Most rebellions have occurred because some individuals felt "cheated" out of power and rallied people behind the cause of getting a better rank for themselves. These rebellions almost always (read always) lead to disaster. Often, what happens is that the people who join this rebellion the quickest get the higher ranks, thus leading to an incompetent leadership and a fast crumbling of the power structure. The other option is that everybody will be given a high rank, leading to rank inflation. This means that General Major Colonel Private 1st Class becomes a regular rank since everybody else has that rank. It also leads to shadow leaders and massive distrust between the actual leading officers, since they do not know where everybody else stands in the actual chain of command. Back to the main topic, charisma is necessary for people to follow a single leader. Without this charisma, lesser members of the guild, who may just be power hungry, could easily disrupt the balance of power and create a power struggle within a single organization. This power struggles creates two camps within the military, eventually leading to the division of that military.
The second major aspect of leadership is the loneliness of it all. There is a massive difference between leading a brigade of 5 guilds, and leading the entire military. This is not the same difference as leading a guild compared to leading a brigade. When you lead the entire military, there is no room for mistakes. All the actions you take are yours alone to take. In the case of a captain leading an infantry, he can blame his superiors for approving a major stupid decision, and it will pass. Sure, the captain and the brigade leader will both look incompetent, but the blame will be shared. However, the big boss does not have that leisure. If he blames his subordinates, he's going to wake up to a mutiny. Sure, you can ask your commanding officers for advice, but ultimately, the decision comes down to you. Also, it does not help that the decisions that you take will affect the entirety of the military, not just a sub-branch, which means that a lot more people will be going after you for stupid decisions. The job of a leader is analogous to the job of the spine in the human body. Sure, there are many bones that keep many different parts intact and functioning, but there would be no human without the spine. You can miss the bones in your arm, even in your leg, but if you do not have a spinal cord, or if it is broken, the whole structure will crumble very quickly. Nothing will get done, nothing will happen.