'"If there was none of this magnanimity in war, we should go to war only when it was worth while going to certain death, as now. Then there would not be war because Paul Ivánovich had offended Michael Ivánovich. And when there was a war, like this one, it would be war! And then the determination of the troops would be quite different. Then all these Westphalians and Hessians whom Napoleon is leading would not follow him into Russia, and we should not go to fight in Austria and Prussia without knowing why. War is not courtesy but the most horrible thing in life; and we ought to understand that and not play at war. We ought to accept this terrible necessity sternly and seriously. It all lies in that: get rid of falsehood and let war be war and not a game. As it is now, war is the favorite pastime of the idle and frivolous. The military calling is the most highly honoured.

'"But what is war? What is needed for success in warfare? What are the habits of the military? The aim of war is murder; the methods of war are spying, treachery, and their encouragement, the ruin of a country's inhabitants, robbing them or stealing to provision the army, and fraud and falsehood termed military craft. The habits of the military class are the absence of freedom, that is, discipline, idleness, ignorance, cruelty, debauchery, and drunkenness. And in spite of all this it is the highest class, respected by everyone. All the kings, except the Chinese, wear military uniforms, and he who kills most people receives the highest rewards."'

--Count Leo Tolstoy, War and Peace, Book X, Chapter XXV

The bare truth of the matter, as borne out a century later in the two World Wars. War should so terrible as to only merit the worthiest causes.

And for information, the Chinese monarchs did not wear military dress only because they didn't have to. No one really contested the strength of the Chinese empire at its height. But that said, Chinese monarchs did wear armour when the occasion demanded of it, such as when they had to lead troops personally.