The eastern kings, true despots who earned a lot of hatred, had to continually protect themselves with a personal guard, more dangerous than useful if the sovereign could not completely trust their loyalty.
Therefore, being a member of the guard was a very honorable position.
The captain of the guard was a very high-ranking official. Among them are mentioned:
Potiphar (Gen. 37:36; 41:12);
Benaiah (2 Sam. 23:22, 23; 1 Chron. 18:17);
Nebuzaradan (2 Kings 25:8; Jer. 39:9, 10);
Arioch (Dan. 2:14), and others.
The captain of the guard and his men frequently had to apply capital punishment to those guilty of political crimes or other offenses.
In Mr. 6:27 "one of the guard" is, in Gk. «spekoulatõr», lit., spy.
Within each Roman legion there was a section of them. In the empire, these men served as the general's personal guard, who made them carry messages and search for outlaws and those condemned to death.
Meaning of GUARD
The eastern kings, true despots who earned a lot of hatred, had to continually protect themselves with a personal guard, more dangerous than useful if the sovereign could not completely trust their loyalty.