The....... the absence of cellphones and GPS to locate people and places, maybe ? Also... Interpol having a strong presence and being relevant and talked about ?
Not in the games, but in the Assassin's Fist series, there's dates given and also the fact that Goutetsu was in WW2. Of course it's "not canon" to the games but that's the only sort of relevant frame I can think of.
If I struggled to the end of my determination, to the end of my way of life with my followers, if the result is ruin, then this ruin is inevitable. Grieve. Shed tears. But you cannot regret.