no, italian mafias (at least camorra and sicilian mafia) are older than yakuza that was formed at the ending of 1800, triads maybe are as old as italian mafias, both formed at the beginning of 1800 and strongly influenced by freemasons
anyway, that's just what i think, in my opinion american mob was the strongest in that period, i read yakuza was at its peak in the 1980, but yes was strong also in 1960, triads were porobably in 1970 at their peak
russian mafia, thieves in law, were formed in the prisons under stalin i think (1950s), but they were just a prison gang at that time
yes there were powerful criminal groups in the 1940/1960 (italian mafia in italy, yakuza, triads, corsicans) but american mob was the strongest in my opinion