King as Commander in Chief

Gemara: Uriya was deserving of death because he rebelled against the king by saying, "My master Yoav and my master’s servants are encamped in the field" (Shmuel II, 11:11).

Ein Ayah: The foundation of a successful kingdom is that the king’s great spirit, which comes from the nation’s best attributes, will impact the entire nation. This spirit finds expression in ceremonial matters related to the kingdom, which are carried out by the nation and its army.
If the king is reduced to a mere shadow of his proper greatness, then even if decrees are made in his name and the army carries out his commands as the sovereign, the spirit of the kingdom will be led by army officers, who use their style to give orders to their subordinates. Then the king is the master of the people but not of the army. The divinely ordained House of David, was able to lead both the nation and the army, who all viewed themselves as subjects of David.
Uriya was one of the people who respected the king’s role in civilian life. However, his internal mindset was to give extra status to the army’s chief of staff, as each national element had its own leader. That is why he gave special homage to Yoav and did not include him in the "subjects of the king," i.e., simpler soldiers. This could cause a major problem in the nation, by lowering the stature of the king, who was anointed by Hashem. In this way, Uriya rebelled against the kingdom.