Did no one think about the security risk?!

[Cleretic]

I'd also add that it was a mark of a good leader to be at the front of battle and see for themselves what was going on. The historical mindset very much followed that a leader has no place leading a military into combat if they were not participating directly themselves. The army would win or fall with their leader, and if it fell, then that was on the leaders head and a new head of state would take over - be that by internal mechanisms or by being conquered.

An ideal that, come to think of it, really explains Hien's presence on battlefields specifically. And is a strong contrast with Yotsuyu, a woman who staunchly refused to ever put herself at risk until there was no other option available.