"So i wonder, where they all big pussys standing on there walls and letting there army do the job?"
As too who lead from the front and who watched from the rear, really depended on what culture you came from and what period of time you lived in. As a general rule the further in history you go, the less likely you were to do your own fighting.
In more Celtic/Germanic and war-like cultures it was very common to join the front ranks of your troops at appropriate moments; as king/general were concidered to be the strongest man present, it was (in theory) the reason you led and you were sometimes obliged to prove it.
In ancient Rome, especially the early Republic period, young officers were expected to be the first one through a broken gate or over a breached wall; that was how they earned honors and gain status and promotion. Thus, many older officers in the back row were the 'well-bred' men who survived the stunts of there youth.
One thing that you have to keep in mind though, is that anything in history that you read about a "king" is going to be highly embelished by the author; whether your deifying a national hero centuries later or vilifying todays enemy that will always be the case. Someone mentioned Julius Caesar in an early post; I'd like to point out that 90% of what we know about Julius comes from Julius' own journals, thus written by the man himself! Or was written after his death when his 'godhood' was had be sanctioned by the government.
So, to bring this long ass post to a close and address the second part of the premise:
"Of course these men would be more powerfull then a single unit, put any king or whatever on the front line and he's waisted"..... No, they would have been just as human as everybody else. The advantages they would have had would be better arms, equipment and training (if they were career military leaders) and a troop of loyal followers devoted to keeping them alive; all of which would of upped their chances of surviving on the front line.
