Complex sentence: Sidorenko's feat was not unique, however: several other Soviet snipers scored nearly as many kills, and Simo Häyhä of Finland is credited with having 705 confirmed kills.
Split into simpler sentences: Sidorenko's feat was not unique, however: several other Soviet snipers scored nearly as many kills. Also, Simo Häyhä of Finland is credited with having 705 confirmed kills.