Here are relevant references from the Books where First Sword is mentioned.
I make no pronouncements on these matters, but report them as I find them.
Arrive at your own conclusions.
I wish you well,
I was asked once if a First Sword necessarily 'needed' to be a leader of a military unit.
This is what I found out:
There are nine First Swords identified in the Books.
1st is Kamchak, of the Wagon Peoples. He was a mercenary and not likely a leader.
2nd was Cernus of the House of Cernus. As the owner and leader of the greatest slave house in Ar at the time, it is not likely that he was directly involved in the hierarchy of the guards in his house.
3rd was Maximus Hegesius Quintilius. Again, as with Cernus, in his position, he too was not likely directly involved in the hierarchy of the guards of Ar.
4th was Bosk. As only one of the Captains of Port Kar, he too was not likely directly involved in the hierarchy of the guards of Port Kar.
5th, Drusus Rencius was actually third rank in the guards. But he was not in charge over all of them.
6th was the leader of a small band of fellows roaming Ar. While he would have been in charge of his small band, he was not in charge of any organized military.
7th we have Seremides, formerly first sword amongst the Taurentians or Ar.
8th was the one of a small group who seemed most capable of wielding it.
9th is Alan, first sword amongst the Taurentians or Ar.
"Six years," said Kamchak, "before I was scarred was I mercenary in the guards of Ar, learning the walls and defenses of that city for my people. In that time of the guards of Ar I became First Sword."
"Place your first sword before me," I said, "that I may kill him."
"I am the first sword in the House of Cernus," said Cernus.
it was a room in the House of Cernus greatest of the slave houses of Ar.
The first sword of the military forces of Ar, Maximus Hegesius Quintilius, second in authority only to Minus Tentius Hinrabius himself
Bosk, my master, first sword in Port Kar
"May I present to you Drusus Rencius, Lady Sheila, my sovereign, he who is first sword among our guards?" Ligurious had inquired several days ago.
I inclined my head to Drusus Rencius.
I looked at the tall, spare man. He carried a helmet in the crook of his left arm. It was polished but, clearly, it had seen war. The hilt of the sword in his scabbard, at his left hip, too, was worn. It was marked, too, with the stains of oil and sweat. His livery, too, though clean, was plain. It bore the insignia of Corcyrus and of his standing in the guards, that of the third rank, the first rank to which authority is delegated. In the infantry of Corcyrus the fifth rank is commonly occupied for at least a year. Promotion to the fourth rank is usually automatic, following the demonstrated attainment of certain levels of martial skills. The second rank and the first rank usually involve larger command responsibilities. Beyond these rankings come the distinctions and levels among leaders who are perhaps more appropriately to be thought of as officers, or full officers, those, for example, among lieutenants, captains, high captains and generals. That Drusus Rencius was first sword among the guards, then, in this case, as his insignia made clear, was not a reference to his rank but a recognition of his skill with the blade. That these various ranks might be occupied, incidentally, also does not entail that specific command responsibilities are being exercised. A given rank, with its pay grade, for example, might be occupied without its owner being assigned a given command. The command of Drusus Rencius, for example, if he had had one, would presumably be relinquished when he took over his duties as a personal guard. His skills with the sword, I suppose, had been what, had called him to the attention of Ligurious.
"Who is first sword?" I asked the leader.
"I am," said a fellow to the leader's left. I was sure then that it would not be he. Too, he was on the leader's left, where he could protect his unarmed side. His strengths would probably be in defense. It is difficult to break the guard of a man who is purely on the defensive. While concerning myself with the fellow on the left, or worrying most about him, the leader himself might have freer play to my own left. Too, I suspected the leader would be himself first sword. In small groups, it is often superior swordplay which determines that distinction.
"Who is first sword?" asked the leader.
"I am," said Marcus. That interested me. It was possible, of course.
Some men enjoy killing, and I did not doubt but what one of these was Seremides, formerly first sword amongst the Taurentians.
You had the word of Seremides, my rescuer, he, once First Sword of the Taurentians.
"Give it to him," said a fellow. The blade was surrendered to him. We took him to be first sword amongst us.
"Conceal it," advised Philoctetes.
Aristodemus placed the blade within his furs.
"This fellow, Alan," I said, "I take it, is quite good.
"Marvelously so," said Seremides. "And doubtless better now, I am sure, than when I first saw him on the Skerry of Lars. I have no doubt he is now First Sword amongst the Taurentians, as once I was."
"First Sword in skills," I said, "but not in rank."
"No," said Seremides, "not in rank."
"Pa-Kur," I said, "is not the state's champion. It is a young swordsman, First Sword in the Taurentians, Alan, of the House of Hesius."