The arms race is supposed to include armor and counters to armor that is natural scientific progression.
When defense won out in the arms race is when we had fortified castles that could defeat any attack. Pouring boiling oil and raining down arrows from relative safety from above. Siege weapons would try to counter it but generally if a city could outlast a siege and not starve to death they won. Fortunately we don't have widespread impenetrable modern bunkers tyrants rule from.
It supported royalty that couldn't be unseated and just had to install towers and castles various places. They were also the primary ones that could afford plate and earlier on chain mail and had a clear advantage against many weapons.
Eventually most of the world was ruled by intermarrying royalty so firmly seated that they established god gave them authority to rule from a birthright taught as a religious tenant. It took hundreds of years to shake that off. Then called mining, or tunneling with gunpowder and blowing up fortifications would lead to a world not controlled by who controlled the defenses. The big artillery that could smash through castles came along as well. Gunpowder actually freed us from that world where not being born royalty made you forever second class.
While weapons too deadly are scary, weapons not deadly enough throw the balance of power into the toilet. We are supposed to evolve with armor and counters to armor.
We have legislation that limits civilian application of less powerful ways to defeat armor though. Something as basic as hard sharp metals, principles behind edged and puncturing weapons going back thousands of years to defeat armor is outlawed in bullets.
This makes body armor disproportionately more powerful than it really is if someone applies basic science.