Military leader is a supreme example of an oxymoron. The rampant misuse of the word leader when referring to a ruler shows either exceeding mental confusion or willful intent to mislead. Another example often seen is autocratic leader. The essential difference between a leader and a ruler is the use of force. True leaders have no need nor desire to use force. Rulers always use force due to the bankruptcy of their ideals or beliefs. Anyone in a government or military position is not a leader. They are rulers or commanders. They are part of the domination culture.
Perhaps the word leader is used in cases where elections were involved in the mistaken belief that a ruler who is elected does not use force. We need to differentiate between rulers and leaders in the hope that the overabundance of rulers and the shortage of leaders may balance out and we may hope to find more freedom.