So, both are swinging a sword and holding a shield, but in mirror image? Wow, that does sound like one side would have an advantage. (not)
First time in combat is the most important time. Any disadvantage would be equal, period, and that should be amply obvious. Screw up the first time, there are no subsequent times. If anything, the whole danged army would wind up left-handed after a few hundred generations if this handedness were of any significance. Clearly, the fact that humans are mostly right-handed and have remained that way for 500K years shows that there’s some genes at work, and that A) handedness doesn’t play any role at all, and/or B) as a society, we don’t spend all that much time killin’ one another.
Berserking Vikings swinging around two-handed battle axes — IOW, an amnbidextrous approach — might seem to have an edge (as it were) over either left- or right-handed adversaries, but then consider the gladiatorial combats pitting myrmidons against more heavily armed opponents.
Bettany Hughes’ “Helen of Troy” documentary
https://www.youtube.com/watch?v=xjwOrbfdOM0
ancient Greek wrestling time index 33:52
chariot and hand-to-hand combat 1:18:00
“So, both are swinging a sword and holding a shield, but in mirror image? Wow, that does sound like one side would have an advantage. (not)”
In a complete vacuum correct.
But in such an encounter, the lefty would have fought (or practiced against) his mirror image many times, the righty much less so, or not at all.
Advantage lefty.